Gavin,
Been thinking about your post - sorry for the delay in posting a reply.
Anyway, here are some good places to start:
For general acoustics information I would consult the
Master Handbook of Acoustics by F. Alton Everest. The 4th edition is out and available through your favority online book supplier or library. I should note that my preference is for the 3rd edition if you can find it used or on eBay. (The 4th is chock full of errors and a lot of information regurgitated from manufacturer websites.)
For prediction of what the room will do, that won't be easy with a non-rectangular space. That's not necessarily a bad thing since - with the help of experts like John, Thomas, and others - you can usually forgo any in-depth modeling.
For measurement and analysis of the finished space, your best bet will likely be either
ETF software from
http://www.acoustisoft.com or the
Studio Toolbox from TerraSonde. My preference is for the latter - it offers a LOT more than just acoustical tools, making it less of a "throwaway." See
http://www.terrasonde.com for more information.
Finally, for references including treatment ideas, there are a multitude of Internet sources. Here is just a small sampling:
http://www.saecollege.de/reference_material/index.html (see sidebar menu)
http://www.soundonsound.com/sos/feb98/a ... ofing.html
http://www.soundonsound.com/sos/mar98/a ... ofing.html
and
http://www.soundonsound.com/sos/apr98/a ... ofing.html
http://www.rbdg.com/newsroom/
For different manufacturers' takes on what you need, the best sites are probably:
http://www.auralex.com (:D My favorite!

Especially note the FAQs, Case Studies and other technical lit.)
http://www.rpginc.com
and
http://www.tubetrap.com
I hope this helps you. Let us know how things progress.
Best regards,
Jeff D. Szymanski
Chief Acoustical Engineer
Auralex Acoustics, Inc.