Does the Heat Exchanger get serviced during a routine boiler service?
It is not part of the service and are prone to blockage. My service engineer volunteered to remove it at each service and wash through under the tap. That would keep most of the blockages at bay. If you have it done at service you are not paying for call out and as it is not a difficult job, need not cost much extra. Ask the engineer to fit a Boiler Buddy. They cost about £80 and fit in the supply pipe. They magnetically attract the iron particles from the rads and you can see if they need cleaning. At which point you isolate at each end, remove, wash out and put back.
i think £ 60 is cheap but that is not normally done as part of a service, i would have thought a good engineer would have replaced the diaghram first, or checked flow switch , there are a few variables here age of boiler etc . as a point of note i will repair boilers if worthy but i do give my customers the choice to replace the boiler of it is more beneficial the reasons for this approach is because EG: say the boiler needs parts and labour which could be £300-00 and it only replaces one or two parts and solves problem in the short term, it may be a model prone to breakdowns due to age / usage etc. then for i will say a few quid more have a new condensing boiler economical , guaranteed and customer are left happy . or do you keep wasting money on repairs.