Stolen trademark? - Urgent

A couple of years ago now, a group of friends and I became fans of a particular book series which has recently become very popular. We decided, we musicians that we would like to create a musical based on these books as a piece of fanwork which we would have made no profit from. If we had somehow made anything we had actually intended to donate it to a charity linked to the books.
We also run a website based around these books which has become pretty sucsesful and which the author of these books and her brother, who runs her official website, has joined. Before we began work we specifically searched to make sure that noone else was planning a similar project as we didn't wish to waste our work and we found nothing. Though around this time we did find that the author on her website had said that she would like a musical to be written at some point.
For a while we tried to contact her using several methods. Unfortunately we couldn't use a personal email address linked to their accounts on our website because, though they have confirmed from official addresses as well as in person that they are members, we wished to preserve their privacy and have thus never looked into which of the 1000+ website members they are. We tried for a long time, stating our intentions in the subject lines of our messages, also sending to publisher addresses as well as to the company that produced the movie adaption of the books, and in that same subject line requesting that someone let us know if there were any problems or objections. Noone sent anything objecting, and so we began to write.
We had planned to have fans from various locations audition by sending recordings of their singing through emails, and when it was cast and the recording itself done we were going to use sound software to edit it all together. In this way fans could be involved and wouldn't have to worry about meeting up with strangers or travelling over long distances. We set up a website and opened auditions, and just to be absolutely sure, sent a few more emails to our collected addresses as well as to a couple of new ones which we found more recently.
A few days ago we got an email from another group basically demanding to know what right we had to perform -their- work. We were not very happy at all with the tone of their email, but we remained calm and professional and explained to them that ours was an original work, that we had not realised that anyone else was working on anything like it, that we had searched to make sure of this fact and that we had contacted the author's representatives. Just after this we recieved an email from a company wishing to help us manage the musical, help out with all the legal stuff etc. and we accepted. She has contact details to the author's agent and publicist and I believe is now in the process of contacting them. Prior to this conversation, as we believed we were writing a piece of fanwork we did not realise that we had to set up any trademarks or companies otherwise we would have done so when we first began our project two years ago. The management company offered to help us set everything up and we began those processes.
Just after our first conversation with this company we recieved another email suggesting that we change our name to avoid confusion and stating that they had begun work last June. We explained that there really wasn't any other name we could call it, we had already purchased a domain name, given out email addresses to fansites to announce auditions and had been working on ours from around November or September the year before their work began.
They -then- claimed that they had trademarked the name and ordered us to change it. The management company advised us to forward their number and request for this group to contact them. We did so and this morning recieved an incredibly rude email back from them in which they refuse to contact anyone and repeat their demand in a very arrogant way. Basically they are trying to bully us into "giving up".
We have tried to be polite, we have tried to answer their questions, which I have since been informed were very unreasonable questions to demand answers to. Their emails are getting progressively more aggressive and really it seems to be bordering on harassment.
I have forwarded this email to the management company but have not yet recieved a response. Our representative is not an attorney and this is the first time we have had to deal with anything like this.
Their own site, we are sure, did not exist when we checked a few months ago before we began to write and it looks rather hastily thrown together. There is a news blog with only one entry which is very vague and claims to be from September last year but of course it may not be. there is what is meant to be a list of songs - Only 12 which is less than half the amount we have planned - and only one of them is actually named. This is named after a piece of music on the movie soundtrack.
If they truly registered a trademark, why did they not say so in their first email instead of waiting several days before bringing it up? And if they have, is there any way that we can contest it and prevent it from being awarded to them?
We do have proof that our work began before the date that they have claimed, but they say they had a trademark notice on the site for it's full term of existence. We looked closely at this site when we recieved their first email with the link contained within and we did not see any mention of a trademark at that time. Furthermore their site refers to an "unauthorized parody" which suggests to me that they have not even bothered to contact the author's representatives. If they had surely it would say "unofficial" instead? Ours is a serious piece of work intended simply for the enjoyment of fans and possibly to support a charity linked to the book series, whereas theirs seems to be a live performance which they don't seem to have announced to any fans or held open auditions for, and which they obviously intend to profit heavily from. Their site actually makes it sound as though their work has been rather heavily influenced by the likes of "High school musical" which frankly would be ghastly.
Obviously we will speaking with our management company but I don't know how much experience they have with this kind of thing and they seem to take a while to respond to emails. In the meantime I'm trying not to have a panic attack and have been looking around at various sites.
The last thing they told us was to register a trademark quickly but the thing is - when they claimed they had registered this trademark I did a search on the trademark database site and ran it through several versions of the search. It did say on those search results that the trademark had not been registered but I don't know whether it includes pending trademarks or not. However their refusal to speak to anyone acting on our behalf and the thrown-together site and so on makes us highly suspicious.
Though it is possible that they thought of the idea themselves without having heard of our plans, there is also the possibility of it and the name having been being stolen from us. These sites tell me I can contest trademark claims but only within a certain amount of time and I do not know when it's alledged to have been registered. And of course with a large fee attached which won't guarentee it being prevented anyway.
We are really just a group of friends who run a fansite. Wev'e never had to handle anything like this before. If we'd realised that trademarks and so on would be necesarry we would have checked that database too before we began to work - though we are 99% sure that when we did begin to write that trademark had not been registered, even if it has been now.
Does anyone have any idea of what we can legally do? Wer'e completely non profit and students so we really can't deal with huge legal fees. I can just about manage the fee for registering a trademark but at this point I do not know if our name is really taken or not and every number I find and call to ask about it is either incorrect or else the "office is closed right now" because apparently noone is capable of running a helpline when people are actually free to -call- it.
Wer'e basically being harassed by people who have -probably- stolen our idea and name who are -claiming- that we can't do anything about it. If that is the case then the whole legal system is ridiculous.

Sorry just to clarify - ours was to be only an audio recording with the possibility of live performances in the future with permission from the author.

Since they didnt mention it first time it sounds like they only just registered it to me.
If the author is on your site you must have a good relationship with her right? Would she see a posted announcement about it when she logged in?
And which country are you in?

I am based in the UK but it was going to be released on the internet worldwide and thw other two writers are American. I think this other group is American since they did mention "US law".
We do have a good relationship with her but since she's so busy we don't get to directly talk with her much. And putting up an announcement would alert other members to the fact that she had registered which could possibly be a risk to her privacy. Also we don't know how often she logs in.
All the sites we contacted including the largest fansites around apparently hadn't heard of this other group's work and they have literally hundreds of thousands of visitors daily, many of whom submit news even if just to see their name on the site. So they basically send in everything and anything even remotely relating go the books or the movie.

Do all creators of fanwork have to contact the original owners? I thought as long as you put up a disclaimer it was ok.

Usually I think it is yes. In fact this particular author sems to encourage many forms of fanwork. People have written songs about the series before and have formed actual bands inspired by them. However since this was to involve other fans outside of our initial group and because it's such a large work we wanted to contact her out of respect for her and her work.

Oh also I forgot to mention - we suddenly got an email from a different address asking if wer'e official and have permission and so on. It arrived around the same time as the trademark email which again seems highly suspicious to me. It looks like they're just trying to dig around to catch us out which isn't going to happen because within our knowledge we've been extremely careful not to tread on anyone's toes and there's really no way that they -can- catch us out.