Meatloaf, sorry I did not understand the ettiquitte.
After watching various utube videos I went ahead with more confidence. I have never seen the inside of a bike clutch before.
I followed some advice I read somewhere and laid the bike on its side to avood draining the oil Then after a bit of a struggle I got out the screws holding the side cover. They are Phillips head screws, not bolt heads. The oil had all drained into the gearbox region which was very convenient! When I pulled out the clutch pack the problem was, as suggested by blackhat250, spots of rust on the steel disks which I rubbed off with 180 grade paper. The fibre disks were fairly worn but I left them since the bike does little work. There are rubber ring spacers between the steel disks. I have not seen them mentioned before. They appear to separate the disks when the clutch is disengaged. After putting it back together all worked correctly.
Thanks for the replies.