OK, so I looked at Google groups and am a tad worried about a few issues that I just cannot find the answer to in their circular "help" files such as maximum post lengths, file storage (for photo's and data) though thats not such a problem and wether the group would be visible to other people. Anyone any ideas on these points? I have been on a couple of yahoo groups before but they didnt really seem too suitable for what we would be looking for. We are currently using a private facebook group but again, its really not suitable for any meaningfull exchange of ideas and there are a lot of issues to be sorted before we get into the technical part of the project so space for writing whilst keeping a record of what is being said without having to resort to emails is what is really wanted, all things that seem to be acheivable on a forum. The ability to edit posts by the author with some form of method of logging that would be handy too. Oh and being able to run polls is also something that would be bloody handy too.
Depends whether you want to keep the IP to yourself, or dump it in a grey area called Google. I'd argue for buying a domain and running Joomla up on it, then install Kunena on it (Forum plug-in) and away you go.
You have Joomla for the big content items and to hold documents you might need to place in it and Kunena to hold the discussions.
Run it on £30 hosting and don't sweat about whether you're handing off your IP to Google/Facebook etc.
Let me know if you need any more advice on this.... I've done a bit of it.
If by IP you mean the intellectual property then yes we would want to keep it to ourselves. As for the rest of what you said, you might as well have been talking Japanese but any further pointers would be appreciated!!

One other small point is that we would be looking to run some form of FTP server for exchanging a variety of types of data. I have a NAS drive that should be capable of doing this but would it be possible to integrate this sort of thing into a forum or would this needa website or something else in the mix to use it?