Well, yes. As I said above, I'd like to know how best to proceed with getting this PCN dropped.
Like most people we see on here, you are not familiar with the legal process; that's why we are all here to help you !!
Essentially all you have done so far is to submit an
informal challenge to the PCN. In the legal process, the owner as per the name and address on the V5C Registration Certificate has legal responsibility for a PCN (pay or appeal), but the driver can submit a challenge. However legal responsibility remains with the owner.
So the only real way to fight an obdurate council is to take them all the way through the process ending up at the adjudicators. Doing this means you lose the discount option, and councils ruthlessly 'game the system' by refusing virtually all informal challenges, knowing that most people, (like >95%) then just cough-up to get the discount, not knowing anything about the legal process, and thinking it could get them into owing serious money.
So now, as the owner of the car, if you're not happy with their response, you have the option of paying the discount, (like >95% of people do), or taking the matter further. This means you must now wait for the Notice to Owner and submit
formal representations as owner of the car, against that. When the council refuse these, you can register an appeal at London Tribunals. From this point on, you would be in for the full PCN penalty. Having said that, most councils, (except Havering), re-offer the discount when rejecting formal representations against a Notice to Owner. The maximum you would ever have to pay is the full PCN penalty if you lose at London Tribunals. Of course if you win you pay nothing.