I had 3 radiators which were not working and worked out that it would probably because of a stuck TRV. Following a suggested solution I tried tapping with a hammer and gentle pulling up the pin with pliers. It worked a treat on the first 2 and then on the final one the central pin came out and is now gentle leaking water! What do I need to do now? Can this be repaired or do I have to call someone out to get it replaced?