the gym has been negligent and you have suffered a loss as a result. your loss is calculated as what? the cost of a replacement jacket of equal quality... dont settle for ?60 - go for ?150. If they dispute say that as you cant decide its best that the courts decide - thats if you are prepared to go to court - or at least threaten to, if not you wont get anything. proof of purchase is irrelevant. you could have been given it as a gift but the loss is still the same - you now need to spend money putting yourself in the position you would have been had your jacket not been damaged - ie., a replacement jacket = ?150.