with a leaking slave will feel judder when pulling away sometimes as the clutch isn't re-engaging smoothly due to hydraulic pressure leaking
if fluid gets on the flywheel or clutch plate it will slip.
my vans release bearing was buggered but if i pumped the clutch a few times before starting the engine i could get around it.
Funny you mention this as the GTI seems really jerky (sometimes) when pulling off but I've just put it down to my poor clutch control

Although I drive a lot of hire cars through work and never have a problem and I've never had a problem with my previous cars
It hasn't slipped for a while now, in fact the day after posting this thread I took it to a local dealer in Cornwall, it slipped on the way there but no matter how we both drove it, it didn't slip with the tech in the car. He basically said it was probably wheel spin

It's slipped maybe once or twice since then, even with all the cr@p back in the car today on the way home, it didn't slip... or if it did, not as noticeable as when it first started. There's also been no "clutch smell" apart from one occasion, which was strange as it wasn't slipping! I think it may have been the car in front as we were going up a MASSIVE hill! I would expect some kind of smell when it does

as I mean it's literally going from 3000rpm to 4000-5000rpm without accelerating the car - that's a lot of "slip"
The clutch pedal also feels like it sticks sometimes when coming back up. I think I mentioned this before in a previous post. Sometimes it doesn't do it, other times very slightly, sometimes quite bad, altho I've heard some people have problems with their clutch pedal doesn't come back up at all and it's certainly nothing like that, you can just feel it sometimes
Thanks for the help. It's booked into VW on 29th although I suspect I am away with work then so may need to reschedule. I'm glad it's stopped for now though as at one point I did think I'd end up breaking down!