How often do boilers break down? I think I have made only a couple of call outs in about 40 years.
The one I remember is the boiler breaking down the morning of my MiL's funeral. It was January, with a temperature well below zero.
I rang my CH service company at 7.30am, there was someone at the house by 8.00am and the pump had been replaced by 8.30. I doubt British Gas could meet that.
To be fair to British Gas, their contract does include the cost of spares and repairs and despite the extra cost is ideal for someone who would have difficulty meeting an unexpected expensive gas repair bill. What was always known as the 'peace of mind' factor. However, if you can afford to pay any unexpected repair bills, you are much better off with a contractor, who calls you every year to arrange an annual service and just charges you as he goes for any work done. It is a lot cheaper.