You can't do anything formally until you receive the Notice to Owner. The 50% discount is the carrot.
Even if you were to make unsuccessful formal reps, it's more probable than not that the reduced payment would be re-offered.
IMO, yourreps would be as per your original - the second go at asking for their discretion plus...
You would hope that the following argument might assist them in their deliberations, namely, about the council threatening the driver, who also happened to be the owner and therefore has first-hand knowledge of pre-NTO matters, with a grossly inflated penalty without explanation or lawful basis. Read the website page and understand:
The driver has received a letter informing them that their reps were unsuccessful, that a reduced payment would be accepted for the 14-day period specified; that if not paid then after the expiry of the 14-day and 28-day periods, whichever is the later, a NTO would be sent to the owner.
But you do NOT know when, they have 6 months. And you don't know what it contains, this is 'explained in the notice', other than that it would be a demand for £160...and then what??? According to the website £240 would be due on 18 November.
Is this what the NTO would contain?
The NTO would be deemed served 2 working days after issue, unless the owner can show that it was not. So timings are rebuttable.
The threat of £240 WITHOUT A CONTEXT available to the person reading it because the NTO contains the details AND HASN'T BEEN SERVED is IMO grossly improper and could represent successful grounds at any appeal the the adjudicator.
Wait for others.