Ive used these before, they have a unit In Blackpool.
They seem competitive on price although I havent used them recently.
http://shop.ebay.co.uk/techniclutch/m.html
As for clutch fitting:
I watched Scoobyteknix fit my old car (5 speed) on a ramp, and without going into too much detail he did the gearbox removal method and it took 3 hours with a brew break and ciggy in between.
At the same time a Classic STI turned up for the clutch install, but also a new water pump and cam belt. He did this on the floor (engine out obviously) in the same time as mine give or take 15mins
Rob