Rushed up to Hull today to help sort a few things out, one of which was Ian's Golf. He'd gone to sell it the other week, for it to die the day the guy came to collect it. Bugger 
Anyway, after several chats with mates in Club GTI, a surf of the forum, the conclusion seemed to be it was the distributor, or more specifically the Hall sender that had bust. Not something you can easily test on the car, but fortunately there was a scrappie in Hull that had a Jetta GTI with a distributor and ECU. I'd thought it's worth getting the ECU, better to be safe than sorry. So, toolbox in hand, me and Nige went there this afternoon to strip the car of the bits we needed. And, best of all, we got the lot for £25 
Even better still, it didn't need all the bits in the end. The easiest part to check was the small black plastic box on top of the ECU. Unplugged the one on the car and plugged in the new one, turned the key, and the car started up Five minutes, and all's back to normal again, hurray
We're all off to get drunk now, full of the joy of fixing the car
