Sorry to dig this old dog up again ... but guess what ... I got a job this morning and the job sheet said '' Cistern wont shut off''.
When I got there the sisten inlet valave was one of these...
http://www.toolstatio...eck+Adjustable+Compac
t+Valve+Bottom+Entry/d20/sd2835/p37311
It wouldn'nt stop filling and just ran into the pan making a noise ... day and night.
I tried to adjust it with the spiral rod, this did'nt have any effect.So I turned the water off... and undid the lower blue nut and lifted the whole assembly out leaving the base part of the valve in the cistern.
The large blue nut on top of the valve was then carefully removed ... this reveals a washer with a pin going through it... there was a few bits of scale in it as well.
It was flushed out, and cleaned up and refitted.
Works perfect now..!