Thanks to you both for your replies. Yes I think it's strange. Looked again this morning and the piston in the old slave is fully out. It has siezed, lots of white corrosive stuff in the area. I can only think at some point I've half forced an already defective clutch/slave and its seized when extended. I've cranked it round on the starter, in first gear and there is no drive to the rear wheels. There is 1 1/2 to 2 inch free movement on the operating lever.
Thanks again..Neil