I agree, Royal mail will CRB check you before they offer you a job. I suspect they will probably credit check you as well. You may wonder why, well, i would say as you are likely to be handling mail, that could well include money (in birthday or christmas cards for example) they will need you to be squeaky clean on the credit front. They dont want to be running the risk of accusations of people stealing mail because it contains money in order to pay off their own debts (not saying it would happen, but you got to see it from their point of view)