my tuppence worth.
We had this person out, that person out (the origonal installer has sadly passed away, but we did like him, but being dead is a bit of an inconvieniance, smells a bit too) it wasn't costing a BIG fortune, but it was annoying not been able to know they would come when asked and FIX IT, or kept waiting becasue the wrong part arrived.
In the end we gave up and got in BG, they charged xx (forgot how much) we then took out their 3star service, being a contracted customer means we get peace of mind and service is usuallly next day and so are replacement parts (pity they dont arrive at the same time
)
I know its great to support the little man, but if you want to go that route, ask questions before you invite them round, like are you familiar with xx boiler, find out something about your boiler (see its manual) and ask does my boiler have a ********* (that you found in the manual) yes i know its devious but it shows if they know what they are talking about. also plumbers are NOT heating engineers, like saying i am an electrician
so i can fix a tv, its electric, but thats where the similarity ends.
as for asking the man in his van, i am not too sure on that one, put it this way,
bloke in van gets asked do you fix xyz boiler. ask devious question, then what is he going to charge, does he have spare part? (probably not, but to be fair you cant expect him to have all parts) ask how long to get say a thermocouple (or any other common part the guys here can suggest)
does the bloke in the van have the right attitude? do you feel "comfortable" talking to him?
I am in no way suggesting the small man in van is no good, you just have to find the right one for you.