Their usual nonsense. See what others reckon but I'd be tempted to respond along the lines of the below:
Dear sirs,
I have received your recent correspondence in respect of my appeal against parking charge ______ for vehicle ______.
Thank you for confirming that responsibility for the charge lies with the driver at the time, and not with me, the registered keeper. As we are in agreement on this point, which formed the basis of my appeal, I look forward to you confirming that my appeal has been successful and that no further action will be taken against me.
As already stated in my appeal, there is no obligation for me to name the driver and I will not be doing so. You do not require any further information to process my appeal and I expect you to make a decision on the information already provided.
Yours,
I have removed that notice as you have left both the VRM and PCN reference number visible. With those details someone could log onto Gemini's appeals portal and cause mischief. Please re-attach with those details removed. Additionally, it is the registered keeper who has received the notice - Gemini have no idea who the driver was, and you should keep it that way.
In the meantime, Gemini are making no attempt to hold the registered keeper liable using the provisions of Schedule 4 of the Protection of Freedoms Act, and have issued the notice too late to do so even if they wanted to. With this in mind, assuming you are the registered keeper, you could appeal along the lines of the below:
Dear Sirs,
I have received your Parking Charge Notice (Ref: ________) for vehicle registration mark ____ ___, in which you allege that the driver is liable for a parking charge. I note from your correspondence that you are not seeking to hold me liable as the registered keeper, under Schedule 4 of the Protection of Freedoms Act 2012 ("The Act"). You have chosen not to issue a Notice to Keeper in accordance with The Act, and it is now too late for you to do so.
There is no obligation for me to name the driver and I will not be doing so. I am therefore appealing on the grounds that I have no liability as the registered keeper of the vehicle. I am unable to help you further with this matter, and look forward to your confirmation that the charge has been cancelled.
Yours,
If you are not the registered keeper, tell us, as a different approach may be needed.
If appealing online, be careful there are no drop down/tick boxes that cause you to identify who was driving, and keep a close eye on your spam folder for their response. If they do not respond, chase them.
Gemini will very likely reject your appeal, because they can. You will then have the opportunity to appeal to the IAS. Some (not unreasonably) regard them as a kangaroo court, that aren't worth bothering with. Whilst I often agree, in clear cut cases like this, where the notice has been issued too late for there to be any PoFA liability, my view is they are worth appealing to - it takes comparatively little effort, and they do sometimes uphold these sort of cases.