I usually try to avoid admitting to working at Halfords (hey, it's on bikes alright) but if I was you, I'd avoid the aircon services on offer.
There's a lot of ill feeling within the company about inadequate/no training, and a lot of stores are refusing to run the service at the moment to avoid legal problems when the minimum wage sales guy breaks someones aircon.
Ok, so some stores are doing it and will do it perfectly, but there's a risk you'll get one of the ones that hasn't had proper training (from what I've heard from on bikes they expect us to practice on staff cars... yeah right), and then I doubt you'll be too happy.
This is all IMO of course.