Yah I get these offers from time to time. Random guy with a cold call offering delicious fluffy clouds in vanilla serbet. You work for some shady bunch connected to BG, but not directly with them, because probably this works out the best for all (but you). BG doesnt have to provide you with anything, treat you as self employed (which otherwise they couldnt do), and while the guys directly under their umbrella are shooting the sht and getting paid decent moneys, you run around and do 6-8 breakdowns a day. You get 45 GBP/breakdown. This is what they expect of you.
I know from experience this isnt possible where I live, because driving from one address to the other can take easily 30-45 min. That leaves you with 15-30 minutes to park the van, go to the door, get to the boiler, take cover off, diagnose fault and repair. Within 30 minutes you must be on your way to your next job, otherwise you wont do 8/day.
I had gas safe guys come to fix my boiler, before I was gas safe. Took them (2 guys came, one BG employee) an afternoon to make sure the fault was correctly diagnosed, and boiler only worked on the 3rd day when the part came in (fan). 1 hour then to remove the old one and fit new one, thats in and out the door basically.
Others from BG came to upgrade my meter to smart meter, they were on it for at least 3 hours. Everything easily accesible under the stairs cupboard, big enough to comfortably work standing up, not crawlin on your knees and elbows.
I do not want to hear 6-8 breakdowns per day bullsht, I know its not possible. One day youll forget something important because always in a rush, and someone dies.