Check your status with MCOL urgently.
If you did not file a defence on time you may find UKPC has applied for and obtained a default judgment against you.
If not, submit a defence as a matter of urgency.
If so, you either pay up or pay >£300 to get the judgment set aside, which will only be granted if the court thinks you have a potential defence and then, if you win, you may or may not get the fee back.