Have you tried the sports shops, they do leisure wear (jeans etc) as well as sports clothes and will usually do youths sizes. I am thinking of JJB sports or the like. Do you not want to get anything by post, or do you just not want to have an account? If you don't mind getting by post, i get things for my kids from laredoute, which is a catalogue or on line, you can set up an account, but I just pay as and when, they do a specific range for teenagers, but it is mainly "named" goods rather than their own stuff.