Update on this. I've just taken it for a decent drive.
I can pull the car in 5th gear without the clutch slipping from standstill, it pulls away easily in 2nd from still.
It goes fine full throttle 1st and 2nd, but if i go into 3rd at low revs and open up full throttle, the revs increase quickly without any engine speed increase.
The question now is , could it be a problem with the clutch not releasing rather than slipping? could it be a problem with the hydraulic system instead?
Cheers.