potterton netaheat problems!

My potterton netaheat 10-16 failed to ignite last week and I asked a corgi to look at it. He replaced the fan and went on his way and my boiler appeared to be back to normal again. However, I soon realised (as in 15 mins later) that the temperature of the boiler was extremely hot and the thermostat knob didn't seem to have the same effect it had had before Corgi got to it so I switched the boiler off. I rang the Corgi and he said on the phone it is supposed to get hot but surely not this hot!??? ! I've turned the boiler off again as I'm scared to use it and am back to the immersion for hot water............any suggestions please???

Forgot to mention that when it was on it was very gurgly in the tank in the airing cupboard and radiators?

mr CORGI is called MIKE BLEEDING THOMPSON

and has and does not wan't nothing to do with registered gas installers

so go and get on the phone to basingstoke if the lad is registered i am sure they will have the skin off his back (all the gits are good for )

if not they will tell you there is nothing they can do