If it goes to court they’ll have to prove their financial losses as you ‘took a space from a paying customer’
Not any more, previous court ruling that it can be of a value sufficient to act as a deterrent without being unreasonable (“a clause will not be regarded as a penalty if it ‘serves a legitimate purpose’ and is not ‘manifestly excessive’ “.
It no longer has to be directly attributable to costs incurred.
https://www.supremecourt.uk/cases/docs/uksc-2013-0280-press-summary.pdf
ParkingEye Vs Beavis
In this case, seems like you have an admission already that you overstayed so not worth appealing on the grounds that you didn’t. There may be other ‘get outs’ such as signage, etc., and other sites can advise on that. But seems to me your best bet is to deal with ASDA / the store directly and ask them to waive it out of goodwill given you can show (I assume) that you were spending money with them the whole time. As the Parking Co in essence work for ASDA, they in the end can call them off.
Ignoring it is not IMHO an option, since the Beavis ruling there is a high likelihood it will be pursued (others will disagree, i wouldn’t risk it) and as said you could end up with a CCJ if you ignore it to the ultimate degree.