What has caused damage to my Renault Clio's new air conditioning unit?

I recently took my Renault Clio 1.2 Extreme into my local Renault dealership for a minor service and its annual MoT. I was advised that the air conditioning unit required a service, and, as it would be cheaper to have it done at the same time, I agreed. Two day later, the first time I switched the air conditioning on, a dreadful hissing sound had me immediately turning it off. The garage told me there was a tiny hole in the corner of the condenser allowing gas to escape. They thought that possibly a small stone had caused it and that I could expect a bill of around £700. As an elderly widow, there is no way I can afford this. Is it a fair charge? And is there some way the garage could have caused it when servicing the air-conditioning?
Air conditioning condenser radiators are usually situated in a place near the front of the car where they are vulnerable to stone damage, but there is a chance that it sprung a leak from being of faulty manufacture. Skoda has been replacing a/c condensers FoC for this reason, so there is a chance that Renault might do too. If not, an independent air conditioning specialist might be able to fit a new one for you for as little as £250.
Answered by Honest John on

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