In reply to FesteringSore:
Was going to suggest BG.
We had years of them servicing and repairing our old boiler and the cost would have been many times the premium!
They always left us a little sticker saying:
"This equipment does not meet current standards" Which was OK as it was an existing installation.
When it did eventually die, we had to get it done to current standards.
BG did this at a reasonable price compared to other estimated gained.