You’ve obscured dates, which we request you don’t do, but you have 14+5 days from the date of the N1SDT form to file a defence or Acknowledgement of Service and, if you do the latter, you have an additional 14 days to file a defence.
You’ve file AoS, so you have the 14+14+5 days for a defence.
If you want to contest the original notice, you can submit a Subject Access Request to the parking company to obtain it. There may be technical issues with it, especially if the driver has not been identified.
You keep referring unwisely to what the driver is going to do. No, the registered keeper is probably the recipient of the notice and is going to contest this. They know who the registered keeper is, but will only know who the driver is if you tell them. If you tell them that the driver has filed an AoS, and they know that Fred Smith has filed an AoS, then you have told them that the driver is Fred Smith.