Thanks for your reply.
It's not possible to even talk to Potterton technical people unless (as people say on other threads) you are CORGI. If you phone, the first thing they ask for is your CORGI reg. no.
I'm in the situation where (due to having just become an unpaid foster carer), we urgently need to fit a conservatory on the back of our small house. We have a Potterton (/Baxi) Promax HE15, 5 years old, fitted to our kitchen wall, with standard short 3° angled horizontal concentric flue. I've...