Every contract is debatable,a ll you need is the right angle.
For example, say I was selling a second hand motor with 4 new tyres and 11 months tax and you gave me a £500 non-refundable "exclusivity" deposit to hold it until you could come and see it. When you rocked up, one of the tyres was bald and the tax ran out in 2 months... would you ask for your £500 back?