my other half is a gas engineer/plumber, he's been to many boilers that BG have supposed to have serviced, he's never seen a good job of there's yet!
People think that because they have a big name and are a national company that they can be trusted, far from it!
If they can't be bothered to fix it they just condemn it saying that the parts are obsolete and give silly prices for new boilers!
Always use your local gas fitter / plumber.
Cheaper than BG and certainly mor reliable.