HI,
Thanks to everyone for your advice. I stripped the entire clutch assembly, filed some grooves out of the basket, serviced the activating worm, replaced the friction plates, cable and lever and the whole thing is working much smoother and lighter now. I think the biggest impact was made by the cable, which according to the supplier was the bikes original cable (coloured grey!).
Thanks again...I'll be back with any other probs.
Keep your feet up.