If your 12 year old car's air conditioning was still working properly having never previously been re-gassed then I am amazed. All A/C systems lose refrigerant over time. Contact an A/C specialist, not any old local garage, who will re-gas it and test the system. They'll also be the best people to advise you on any necessary repairs. VCDS can be used to test the components of the climate control system, but it won't tell you it's low on gas, or if you have a leak.

Cars built from aroumd 2016 (some earlier) use the new Yf gas which is around £100 per kilo. Majority of cars have a fill charge of approx 500 gms. You need dedicated equipment to prevent cross contamination of the gas . Although operation is the same, the coulpling ports are different. As for hybrids,although the gas is the same,the iubticant is specific because the a/c compressors are electric motors rather than belt driven from the engine.Any contamination with incorrect oil is enough to reduce the integrity of the air con pump/motor. I guess this is too involved for most workshops dealing with a/c repairs.macsworldwide.wordpress.com/2012/03/30/use-caution.../

Update. No fault codes were recorded so took it into ATS today for a re-gas. £29.50 via a Groupon deal. They were honest enough to say they're not experts and it just gets hooked up to the machine. Working well at present and we'll just have to see how long it lasts.