Why does the pressure keep rising?

I recently had my bathroom tiled, in the process the builder took the radiator off of the wall, after refitting it my hot water kept running hot, then cold, then hot, i questioned him on this and he said the boiler pressure had fallen when he removed the radiator, he came back and increase the pressure using the pressure valve, since the hot water has been fine but now the boiler pressure keeps rising even when the CH or water is not in use, usually 1 bar in 8 hours, i then have to bleed the radiators to reduce the pressure but 8 hours later it has increased, when it gets to around 3 bar i panic, we have had a corgi guy out and he serviced the boiler and removed a loop that connected two pipes, he said it was not needed once the system was full, we thought this may have cured the system but it is still rising at the same rate if not slightly quicker, i have spoken to my builder and he says its the pressure valve? i have read some similar questions and could it be my heat exchanger?

Lee
October 2007