You could simply reply with the following;
Charging Notice Number -
To whom it may concern,
I write in relation to the above Charging Notice which I recently received.
Unfortunately, I was not the driver at the material time.
I understand that there is no legal requirement for me to provide further information to you and I will not be doing so.
After taking advice, and not withstanding the above, it's my understanding that there is no viable contract between VCS and the vehicle driver which would allow you to send a speculative invoice.
I am sorry that I am unable to help you further.
Best wishes,
xxxxx xxxxxxxx