Is there anyway of pushing back on this or do I just have to pay it?
No, you don't just have to pay it.
You submitted reps but seem to not have received their rejection. In these circumstances, you need to wait for the Order for Recovery, (adds £9 to the CC amount), and then submit a Statutory Declaration that you submitted reps but did not receive a Notice of Rejection of those reps. The matter will then revert back to the PCN stage.
So, do not pay the CC, but wait for the OfR. If you have mail difficulties, wait until the period to pay the CC has expired, then, after about a week to ten days, contact TEC to enquire whether the PCN debt has been registered. Once it has, you can submit a Statutory Declaration even if the OfR hasn't been receivecd. We give this suggested procedure because one doesn't want to miss the OfR and lose the opportunity to submit an
in-time SD.
Is the address on your V5 correct and identical to that on the CC ?