Thanks Greg.
As it had the original piston, I concluded that the bearing was standard too. I was busting a nut to have this bike at Harrow, but it turned to poo on the friday night before the ride. Having clearly stated that I needed stepped thrust washers made some3 weeks prior (and being promised that they were not going to be a problem),I was left dangling when I received the call that "your L/E bearing is too wide..... and I haven't got time to make them!".
Anway, I digress...Thanks for the replacement info, will make it VERY easy to get another when the time comes.