ORAC, I'm also looking at getting a Mac mini to use as a home entertainment device and have been going through the same conundrums. I can give you my 2 cents worth, but not to all of your questions.
The mini itself - you may be able to get away with the single rather than duo chip. Ultimately, it depends on what you will be using it for. Simple PC tasks (Office, web, iTunes etc) you should be OK with the basic model, but for more intensive tasks, go for the duo.
In terms of the RAM, as with any PC, you will benefit from more RAM than less RAM (sounds obvious, I know). From what you intend to use it for, 512 should be OK, but personally, I would bump it up to 1GB.
Toast - do the UK minis come preloaded with iLife? If yes, then there is DVD burning software included in this set up. Which reminds me, you will need a superdrive rather than the combodrive. The superdrive is a DVD recorder whereas the combodrive is just a CD recorder.
I can't comment on Boot Camp, as I don't have any plans to XP-ize my Mac.
I've been looking at forums on
www.123macmini.com for hints and tips.