(UK) Who on earth can fix my broken flue pipe

Okay so this time two weeks ago I didn't even know what a flue pipe was and now its all I think about.

From what I understand a hole was drilled into our flue pipe, a while back, and sealed with a plug. The plug has somehow fallen into the pipe and left the hole exposed. This was found at a routine gas safety inspection last week. As a precaution our boiler has been shut off and we have had no heating (luckily have an immersion for hot water).

Now we have had three engineers round one from the gas company who found the fault, the man we usually use, who fitted the boiler, and another from British Gas homecare. All say they aren't covered to fix it, can't fix it or just wont fix it and leave. It seems to be some unsolvable problem.

Ive been told it's because it's actually not a boiler issue but then Im told its because they can't work on a Keston boiler. Can someone reccomend if there is anyone out there who can just come and sort this or is the place going to be without heating forever because no one on the planet has anyway of fixing it.

Sorry if this is the wrong place but at my wits end here.