Great machines. Have one myself. Parts are actually fairly easy to come buy second hand and surprisingly cheap. Just get yourself on the GTIROC or GTIR motorsport forums. They have just gone through the cheap stage so the bulk of the neglected ones have been bought to strip for parts or bought by yobs to thrash which in turn blow up or crash. Thus also end up broken for parts. They are seaming to creep back up in value, nothing big as I don't think they ever will go up that high, as they never really did reach much of the Iconic status their performance deserves. But at least going back up is a positive.
I would definitely go for one at the moment. Seam most around for sale are reasonable condition. Plenty of decent ones float through the OCs and Forum for fair prices. I can see them going back up to a generic value of £4-5k where there will be plenty dogs about asking for premiums because "thats what they go for these days" scenario.