Thanks Chris, in reply to the question "how long did it take" , if you meant the actual job it took me around 6 hours from start to finish but thats including a 1 hour break to pick up my son and his drum kit from a friends house. If you meant from the start of the problem it was about 4 or 5 months! I left it because the boiler was working apart from the leak and didnt want the inconvenience of having no heating in winter if my efforts had failed. Anyway its done now and I have just disconnected the filling loop to see if that cures the pressure rise. It does appear to be dripping so I'll see what happens over the next few days and let you know.