If the judgment in your favour has been set aside then the payment by the defendant will be taken to be a payment to settle the claim and as such would not include an automatic right to your costs since settlement figures are invariably less than the total value of the claim.To enforce the costs you would have to reinstate the judgment and he will argue that you accepted the sum he paid in full and final settlement of your claim.
I hope this clarifies the position.If there are any further points please reply.
I have been told by the court, that the judgment was automatically re instated, as he had not put a defence in by 22nd Feb. His cheque was dated 15th Feb, having accepted this would we have accepted the debt as paid
He will argue that having cashed the cheque you accepted it in full and final settlement .
You can argue that you accepted it as a partial payment but unless you said so in writing at the time then there is a danger that the court will side with him on this issue.
Given the amount involved I do not think that it is worth the risk.