Give British Gas a ring, we get slated on here, we're not cheap but we're really very, very good!
Bet that will boost your Qudos points ( £ in the pocket)
Yes I am a ex British Gas empolyee and I think that the way that you are expected to SELL is complely unethical I walked out of a team meeting because of the sales patter I was told to use by the "sales champion" and told them to insert the job where the sun does not shine shortly after
Get a good local Gas engineer to give you a quote