I think you need to help us try to fill in some of the blanks here.
You received the original Notice to Keeper, we assume, because you manged to appeal it. Have you, at any point between then and now, changed address?
As well as receiving a Letter of Claim, you should also have received a Claim Form, from the court, prior to the judgement in default that you have shown us. The Claim Form looks somewhat similar to the judgement in default, but says "Claim Form" in the top left. Did you receive one of these?