getting £550 court fee only back

Sorry if I'm asking a question that's been answered clearly elsewhere, I've had a scroll through the threads but could not find quite my situation which is fairly straight forward!

I applied for divorce on the grounds of respondent's unreasonable behaviour which has not been defended and judge has granted decree for entitlement and I will send for the absolute mid-November. I asked that respondent pay the costs (which are the application fees of £550 that I paid to get the divorce going and we have both not used solicitors as had nothing to divide) and the judge has agreed that respondent is at fault and is to pay the costs.

How will these costs be recovered once absolute goes through - will the court chase the respondent for it like a court fine? Can the respondent get away with not paying it (as is threatening to do) simply by not replying to anything?

The court won't deal with it unless you make an application. First the costs have to be quantified. This is referred to as assessment. There's a process for that. Once the costs have been certified in a specific sum, you can apply to enforce payment by one of the various methods.