Capital One - Rebuild or not Rebuild?

I had applied for a Capital One CC and was approved with a £200 limit - probably because I'm not on the electoral roll and I have no other discernable credit. I thought it would be the card at 29.9% for purchases and BT.

Well, apparently not. Its 0% for 6 months for purchases and 6.9% for the life of a BT. Why do they give me the interest for a good credit history but the credit limit for a poor one?

I'm confused!!