Try this.
Dear ****,
Cheers! for your “Letter Before Claim” dated ******, received with your ref number **** for alleged parking breaches.
Please be advised that I have absolutely no intention of paying these extortionate and ridiculous made-up sums of money for allegedly breaking some imaginary contract which I never entered into and which you have not demonstrated how I personally became party to.
You do not even have the identity of the driver who had the vehicle on the alleged date of offence, yet you want to litigate against me.
I could go on but it is enough to say that this whole claim is utter nonsense and I’m sure that any Judge would agree.
Should you wish to proceed with this farcical claim, then i will be requesting unreasonable costs order under CPR 27.14(2)(g)