Range Rover Classic Clutch Slave Cylinder

Hi, I recently replaced the clutch flexible pipe on my 1977 V8 manual Range Rover. As expected from previous experience it was a pain to bleed the system. However something has happened that has never happened before. For after much bleeding the clutch pedal went hard. Following investigation the piston in the slave cylinder had reached the end of its travel in the bore and the lip of the rubber piston seal had partially turned inside out, thus jamming. This has happened two more times using new slave cylinders. My clutch was working perfectly before I replaced the rubber hose. Pictures in my manual suggest that the slave actuating rod remains in place when the slave cylinder is withdrawn from the bellhousing however mine comes out when I withdraw the slave cylinder -should it be attached to the clutch release bearing arm in some way? Also photos in my manual suggest that original Land Rover slave cylinders had a circlip to retain the piston in the cylinder bore - replacement parts dont have this ?