Overstaying my welcome in a supermarket car park

[Skyedriver]

I know the rules change a couple of years ago so please help.
Arrived at supermarket about 13.30 today. Called in shop, returned to car and it wouldn't start. My battery pack also failed to start it. Would have bumped it down the slope but car park too busy.
Had to be somewhere else so we walked. Returned back to car about 16.00. Car park pretty deserted so my son and someone who arrived for the (closed) shop gave it a shove and it started.
So we were there about two and a half hours. Car park clearly stated that the max stay is 2 hours and in excess of that will cost me £70.
A few years go you could just ignore the repeated letters (that I'm expecting).
What are my options now: ignore, plead broken down, just cough up, offer a more realistic sum than £70 for half an hour?
Thanks for any legal guidance.
T

[Skyedriver]

pim said:

You might not receive a letter.Sounds a genuine case,one thing it does pay to be part of a breakdown service often cheaper than a fine.

We are and also wife offered to abandon watching the tennis and come down with jump leads to be honest but we were due elsewhere at 14.00 and walked...
TBH I was just in a bit of a tizz with young son in tow.

[Skyedriver]

TooMany2cvs said:

Did you speak to the supermarket's customer service desk at 13:30ish? Not only would that have got you logged, so they cannot accuse you of making it up later, but it may well have got you flagged as being parked with an excuse, so don't issue an invoice in the first place.

No i didn't but doubt they would have been interested. In hindsight yes I should have.
I have the receipt for the store purchases.