You need to use a registrar for registering/renewing domain names. Several are recommended on this board including Godaddy, eNom and Dotster. Depending on the number of names you want to register, you should be able to keep annual fees below $10 for .com, .net, .org.
If you want to pay in Sterling, I'll register for you and give you a control panel to maintain your details. I'm in Hampshire/Surrey in England.