The thing I have found with BG guys is if they are one of the good bunch they can fix your problem quite quickly and competently. Why shouldn't they when the company backs them up with millions of pounds of investment in the industry and years of experience.
The problem seems to be the management which filters down to affect all including the customer in a bad way. The installers, I don't know whether its because they mainly use Sub-contractors or because the training is **** (I doubt it) but pretty much all their install work I have seen is not at all to a standard I would be happy with if it was my own work but they don't care, they will probably never return to the customer themselves it will be the service engineers.
The recently trained ones do an NVQ level 3 in Gas in just over a year. Mine took 3 years, why are they allowed to do this, because they are BG! The thing is I also learnt all the relevant building regs, how to lay water mains, designing and installing heating systems, running a business and other things which the current BG guys do not do on their courses because they do not need it. Maybe BG keep there guys working for them by intentionally not teaching these things?
However they do not need to know about that in the day to day gas repair business, they are there the majority of the time to "safety check" your gas appliance and repair it when necessary which they are usually very competent at.
I am sure we all see failings in BG and independents nearly every day, I know I do but sh!t happens, the general public loses out unfortunately!
Just today I saw an Independent who had core drilled the new boiler flue hole and just placed the core piece into the old flue hole, no mortar mix even!
How many new boilers do you see with the flues sticking out to far because Independents are too lazy to cut them down!