Skoda fabia elegance, 2nd hand, air con issue, advice please

Hi there,

I'm new to this forum and my Dad suggested it might be worth a try asking for advice.

I have just got (June) a 2nd hand Skoda fabia elegance, 2011. When I picked it up, the air con worked great for the first 10 minutes or so then stopped and was just blowing warm air. (Temps outside were high 20's maybe early 30s).
I took it to Halfords which ran an Air con diagnostics:

Results: System has pressure leak, system appears to be low on refrigeration gas and recommended to be fully evacuated and refilled using r134a
Which they did, along with fitting an antibacterial canister and said it was all fixed/working in the garage.

I went to pick it up and it did the same thing, worked for ten mins or so and then stopped.
I took it back, they couldn't find a problem, it worked for them in the garage, they ran it for 30 mins and still no problem.

I pick it up, drive it home and the same thing happens, it stops working after ten minutes.
The garage doesn't have any answers/say they can't do anything more as it works for them.

Has anyone had a similar experience and /or could you suggest what else I could do to try and get this fixed?
Obviously with the hot summers/temperatures only increasing I'm keen to get is sorted,

Thanks so much for any advice.