Normally a deposit would not be refundable because the whole point of it is to compensate the vendor if you fail to complete the deal. But if he wrote on the receipt that it was refundable if you couldn't get finance then he has to return it. You can go through Small Claims procedure to try to get it back without having to take the case all the way to court. See: www.gov.uk/make-court-claim-for-money/overview