[Ben O Brien]

Its more than likely leaked its refrigerant,R134A im guessing,i dont know much about air con but one of my dads business' do air con so picked up a bit over the years,
I couldnt tell you where the leak is most likely to be though,im not that familiar with 850 air con,
The reason it was 140 quid was the price of the gas,its really expensive,
I have put a custom aircon system in my 242 and if the 850 system is similar my guess is the condensor is cracked,but as someone already suggested it may well be the dreaded evaporator...