If you claim that there is no appropriate signage that prohibits parking on the grass verge or even parking outside of a marked bay, please gather photographic evidence of the signs. It is the signs that create the contract between the driver and the operator.
You may want to mention to your angry wife that what she has received is definitely not a fine. I will give you £100 for every instance of the word "fine" you can find in the paperwork.
The Notice to Keeper (NtK) is nothing more than a speculative invoice from PPS for an alleged breach of contract by the driver. If she is tempted by the £40 "mugs discount", then perhaps I ought to send her my own invoice for £100 with a £50 discount if she pays it nice and quickly.
If the signs are as you claim, then there cannot have been a breach of any contract. No contract, the "invoice" is invalid.
You may want to edit your wording so as not to identify who the driver was. Use wording such as "The driver rushed my son to the doctors...". No "I did this" or "I did that". Only "the driver did this or that".
Only the driver is liable for the invoice and PPS have no idea who was driving unless the Keeper blabs it to them, inadvertently or otherwise. The Notice to Keeper (NtK) is not fully compliant with all the requirements of PoFA to be able to transfer liability from the
unknown driver to the
known keeper.
So, if you feel that the PCN has been issued unfairly and you (in your wife's name as the Keeper) are prepared fight this, then do the following...
Plan A, porch the medical centre management and ask then to get the PCN cancelled. If they are the contractor of PPS then don't be fobbed off with the excuse that you have to go through the PPS appeal. If they try that, ask them who is the Organ Grinder and who is the monkey in their contractual relationship with PPS.
If the doesn't bear fruit, when near the appeal deadline, make a Plan B appeal with the following to PPS, only as the Keeper:
I am the keeper of the vehicle and I dispute your 'parking charge'. I deny any liability or contractual agreement and I will be making a complaint about your predatory conduct to your client landowner.
As your Notice to Keeper (NtK) does not fully comply with ALL the requirements of PoFA 2012, you are unable to hold the keeper of the vehicle liable for the charge. Partial or even substantial compliance is not sufficient. There will be no admission as to who was driving and no inference or assumptions can be drawn. PPS has relied on contract law allegations of breach against the driver only.
The registered keeper cannot be presumed or inferred to have been the driver, nor pursued under some twisted interpretation of the law of agency. Your NtK can only hold the driver liable. PPS have no hope at POPLA, so you are urged to save us both a complete waste of time and cancel the PCN.
When that is rejected, come back for instruction on how to make a Plan C appeal to POPLA.
In the meantime, please show us some photos of the signs at the location.