I've had everything looked at and the plumber is dumbfounded. He replaced loads of stuff and didnt charge me as he couldnt stop it (nice guy)
You can make it click by moving the loom. Like jump starting a car. Evertime you touch the cables it clicks like hell.
On onther forum someone...
Hey there. Got a Potterton NetaHeater Profile 30e Boiler which makes a repeated clicking noise when trying to fire up. Pilot comes on then clicking starts. Boiler fires up but then keeps clicking and then switches off.
I think its the wiring loom at the front, but I dont know what thats...