Anyway, I put a small patch of rubber on each contact point of a household G-Clamp and it worked first time!! All I have to do now is find a damned rotor-puller. 20mm thread I think. Anyone got one??
Just found an old 20mm oil-filter bolt (from the CB250 itself) and used that as a rotor puller. Worked a treat! I like finding things around the garage that can be made to do the job of an expensive "Special Tool" like the £36 "07733-002-0001" from David Silver.
Just for the search engines...
How do i remove the rotor from my Honda CB250N Superdream? Honda Part No : 07733-002-0001 CB250N Superdream "Rotor Puller Tool" can be replaced with a cheap oil-filter bolt from a CB250N Superdream.