Gledhill engineer bristol area

Hi
I am trying to find an engineer in the Bristol area who knows their way around a Gledhill Systemate III system. A local engineer fitted a new boiler, new hot water pump and new central heating pump, new PCB, and new three way port valve. But I am still having issues which concern me and would like an expert to check things over and correct them.
The boiler makes constant clicking sounds, the water is scorching hot. The pumps seem to be on the whole time and despite having a new three way vale fitted (which sorted the problem of heating radiators when off) this problem has returned.
So I believe the only way to deal with this is finding an engineer who fully understands how these operate.
Thank you
JM

Are you sure the bloke fitted a whole three way valve, and not just the top (motor) part?

This sounds to me like the brass part of it has jammed.

Mike