I suggest buying a mk2 and not a mk1. I payed £800 for my 2000 mk2. It was a cat C with front end damage.
IMHO a better choice than a beaten down old mk1 with who knows how many miles.
A low mileage 2000 Icon sold on ebay a few weeks back for £965. It had a tatty interior, rotten sills and slashed softtop, but they come with a 6-speed and Torsen! If you wanted, you could even keep the airbag (if that's not against IVA rules or something).
A bonus is that the mk2 has an electronic speedo so you won't have the usual troubles with the mk1 cable.
The mk2 is similar enough that it doesn't matter when building the kit.
There's also an oem immobilizer and possibly ABS (yes, it works fine on a Westfield).
The only thing that didn't fit on mine is the stock airfilter box (it's a bit bigger on the mk2), but I replaced it with an open airfilter .