I have put a new bathroom suite in and I now only have hot water supply. The cistern is continuing to fill from the cold mains however. Any suggestions?

It sounds like you have disturbed some crud built up on the pipe walls and now it's clogging the inlet ports of your faucets. Shut the water off and take the cartridges out and check and clean the inlet ports. Now turn the water back on for a minute to flush out the cold water supplies. Let me know, Tom