I've heard of this sort of thing happening before, and although I don't know how the law works on this one, I'm sure that you WILL have to pay up. If it was me, I'd write a letter of explanation, and then offer whatever you can afford per month, in order to catch up. You could probably pay by payment slips at a bank or Post Office, but it's quite possible that they'll want to see proof or earnings, to help them to work out what they feel you can afford to pay back per month. Don't leave the problem. The sooner you contact them the better.