Hello, sorry for not replying sooner, i replaced the small pcb board - part number 0012cir06010/0, from LPS supplies (on web) very cheap (£54.73 incl del.) and arrived quickly, this solved it
That's what I thought it might be. My mate has got the same bolier, i'm going to swap that part over to see if that's what the problem is, but do you think that it might cause a problem in his boiler?