Hi Chris,
The first thing you need to do is to check that you have some free movement on the clutch operating arm. To do this, remove the cover plate from the bottom of the primary chaincase, to give access to the lever. If there is no movement, the operating lever is probably running back until it contacts the bottom of the ramps on the release mechanism. If this is the case, you will need to remove the flyheel to gain access to the release mechanism - the fixed part of which is just a ring with three rollers attached - the crankcase has dowel that locates in one of three slots in the back of the release ring - to gain more clearance, you will need to turn the ring in an anti-clockwise direction.
To get the flywheel off, you need to unscrew the large chrome nut in the centre of the flywheel - this retains the spring pressure plate and 6 springs. With that removed, you will find a special crankshaft nut that incorporates the extension that takes the chrome nut, and the nipple for lubricating the clutch release - this nut should be retained (loosely) in the flywheel by a screwed collar in the counterbore in the centre of the flywheel. Unscrewing the nut self-extracts the flywheel. The flywheel should come away complete - leaving just the release mechanism in place.
If you already have some free movement of the lever, then you may just need to load up the springs a little more by screwing the large chrome nut in a little further (don't do this if there is no free play, as it will put a permanent load on the release bearing, causing premature wear).
Hope this helps,
Regards,
Eddie.