I'd be inclined to just abandon the aircon then ( like I did a few years ago now ) ...... and see what the next lot of MOT Advisories might be
what were the last MOT Advisories ? and at what miles ?
mine's now turning 219k miles and this last 12 months I spent @£2k on 4 x new tyres, cambelt, pulleys, waterpump, Toyota/Lexus UCAs ( all 4 ) and drop links at the front , oh and a full service and MOT incl front discs and pads too .......... she's good for another 10 years and 100k miles methinks
lived beside the seaside for at least 10 years too and no rust to speak of I believe
Malc