IMO,
As far as I can see in the circumstances of your case the grounds would be:
'The penalty charge exceeded the amount applicable in the circumstances of the case';
The circumstances being as follows:
You were aware of the Temporary Traffic Order requirements and had planned to move your car on Sunday evening to an adjoining road reserved for permit holders.(the restriction came into effect on Monday 14th)
Matters did not go to plan, however.
At *** on Sunday my father had an episode of rectal bleeding. I am his carer and contacted the hospital who advised us to bring him in immediately for examination. Unfortunately, my car would not start and therefore I had to call upon my neighbour **** to take us. We arrived at the hospital at approx. ***. My neighbour returned home(could you have called them later to pick you up?). My father, who is 77, was admitted and was in severe discomfort. As he also suffers from a neurological condition similar to dementia and is not able to manage interactions in a hospital environment. I therefore felt it was essential that I remain with him. At this time no-one knew for how long he would be kept in but in the event he was not released until *** on ***.
My circumstances were therefore:
Had my car started, then it would have been parked at the hospital and not on the road and the contravention would not have occurred. But it didn't start.
Had my father not been taken ill, not been admitted and only discharged at ** on ** then we would have returned home on Sunday and I would have called assistance to get it started in order to move from the location in order to avoid being in contravention on the Monday (which I did once we arrived home - see attached). But he was taken ill and admitted.
I respectfully submit that the above support my representation grounds and that the PCN should be cancelled.
Only write what's true and provide supporting evidence as per your initial reps.