Thanks KeefyB.
I've had the 800's clutch apart this evening. The plates looked fine, however, as a precaution, I fitted the pack out of my spare engine. I tried fitting an extra plate in but, there's no room for it - it locks the clutch up solid because it removes all clearance from the clutch - it looks like Ducati fitted extra plates to cope with the increased shove that it puts out anyway. The problem would appear to be the exceedingly gay clutch springs that Ducati have fitted to appease the whingers who complain about heavy clutch action - they are so lightweight. So, I popped in a proper set of manly 748RS springs. Result - much heavier clutch that is hard work
It shouldn't slip now - if it does then it's a set of Barnett plates next.