You have two options to sign Aaron Martin during the first season. You can either try to make a bid, Espanyol could be accepting a 19m bid with the addition of some clauses. They could demand a percentage of profit from next sale (around 50%) or some other clause that could cost you some money in the future. Or, you could just pay-up his release clause (22m). That way you will not be bothered by any other demands by Espanyol.