Freon has a special effect on the atmosphere beyond the "greenhouse effect". Its decomposition into Chlorine and recombination with Ozone O3 is (or is not) a different problem.

Its manufacture was banned by the industrialized nations. Some may actually ban its use, but it is widely manufactuered around the world and on Tech sites I have heard stories of shops using Freon to blow out stalls.

Those issues aside, I wonder why the first shop said that you should upgrade. It would be a real salesman that would suggest that one take an operating R12 system and do anything to it. I must conclude that the system has a leak and is low on refrigerant. If this is the case your most important concern is to get the system fixed properly. Dealers make poor refrigeration specialists as they use so little of the arts of the trade. They repair nothing (only replace) and they seldom use sophisticated leak detecting; using a shotgun instead.

Its too bad our british friend has such poor respect for our independent auto repair trade. Many consumer groups (not industry affiliated) conclude that the consumers best dollar value and highest confidence rate are with the independant repair specialist, not the franchised dealer or other franchise outlets such as tire and exhaust shops.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician