I suspect Kwik-Fit haven't the ability to tackle any repair work to aircon systems, but can re-gas them. So, instead of looking for the reason it needs re-gassed, all they'll do is re-gas them, get the money and can't care less about whether it all leaks out again after a day or two.
"Shall we do a brake check while you're here. It's free". Bet the repairs that need doing aren't though. "Oh we've done your free brake check and your braking is very poor. Lucky we caught it. It needs new pads and disks all round". Funny that, they were okay when I came in.
A cynic, moi?