So, we arranged for an independent boiler engineer to come and look at the boiler, yesterday at 9am. He did not arrive ! I called, he was busy on another job but promised to come at some point during the day. He finally turned up at 2.15p.m. I was not best pleased that he was so late but he was very polite and had his twin sons with him, who were also very polite.
They checked over the entire system, even climbing in to the loft and turning the central heating and hot water on multiple times, they checked the boiler again ! Eventually, they declared there was nothing wrong but a little valve must have got knocked during the previous service. I checked that the hot water was really working and sure enough it was !
All of this took about 45 minutes and when I asked how much they would charge they said £40 plus VAT if I would agree to have the boiler serviced by them next year. Of course, I agreed ! So, the £40 from HomeServe as compensation, paid for the visit and I paid the VAT. Making the sum cost of fixing the boiler, £8 rather than the £95 HomeServe wanted to charge. Also, it was clearly their fault rather than being a new breakdown.
I'm so glad that I shan't have to go through all of that next year, fingers crossed !