Sorry to cut to the chase, but will you pl get away from exemptions to 'footway parking', they're irrelevant in this case. That offence is statutory and doesn't require any signs, a driver is presumed to know as a condition of holding a licence.
The allegation here is that you committed an offence under s137 HA.
137 Penalty for wilful obstruction.
(1)If a person, without lawful authority or excuse, in any way wilfully obstructs the free passage along a highway he is guilty of an offence and liable to [F1imprisonment for a term not exceeding 51 weeks or] a fine [F2or both].
Local authorities are able to deal with this under Deregulation Powers i.e. FPN, but the offence remains the same. So IMO the question is: who is liable?
And IMO it's only the 'person[who] without lawful authority....obstructs free passage..'.
IMO, don't argue the toss about what is a subjective matter, why are YOU being deemed liable? The events happened 5 months ago.
Assuming that this is absolutely the first you've heard of this matter, I'd go back to the named person and:
Refer to their letter;
Say you've looked up the relevant section and ask why the council think you caused or permitted the car to be parked in this way. The events took place over 5 months ago and this is the first you've heard of the matter. You cannot be expected to know who was driving at that time on that day (does your wife drive the car) any more than the council does. In addition, even the events as set out seem conflicting because the location looks like if it's situated in *** Road whereas .......
You'd like clarification.
And stop* parking there unless you want to risk a PCN for footway parking.
*- you or anyone else driving your vehicle because footway parking is keeper liability, not 'person' (driver) as in HA.
Are you the registered keeper of the vehicle.