Thanks for replying Richard. I think you're right about incorrect installation. I've seen a number of posts regarding wiring i.e. converting from 3 to 2 wire. I've now ordered one so hopefully it should be ok. At just over £20 including postage, I think it's worth a punt.
My old drayton Digistat has gone faulty and I find the new model has a small display so I'm thinking of the Salus RT300. It seems cheap so is it any good?
I am about to have British Gas fit a new boiler for me. Amazingly they were the cheapest quote. Maybe all the independents near me are overly expensive.
The question is do I go for a Worcester/Bosch or a Potterton. The Potterton boiler is cheaper and the install simpler (apparently). I would...