Hi folks. I`m not too hot on combi boilers!

My problem has been esculating. When the hot water tap is turned on
you get a bit of hot water then usually when you turn it off you can
hear a huge pipe vibration. The pilot light then has to be
re-ignited.

The radiators also appear very hot but that maybe a red herring.

I have had a bit of experience on a normal boiler and changed a
thermocouple (?) before. Docombi boilers use thermo couplers? Is
that the fault? How easy are they changed on this model (Potterton
Puma 80)?

An embarresing fact is that I can`t work out how to remove the boiler
cover. Please help.

Thanks in advance.

Tc