I got a letter today saying I had been issued a parking ticket at my local Asda (I never found one on my car) and as the discount period was up, I now have to pay £70. 
At first I was a bit confused about how you get a ticket at Asda, but it seems it is from parking in a disabled bay with no badge. However, the only time I have ever done this was when I took my disabled friend shopping. She doesn't have a blue badge, but is a wheelchair user who gets higher rate mobility DLA (so has a car from her DLA) and cannot walk a single step unaided. She needs to be in a wheelchair to shop.
At the time, as we didn't have a blue badge I asked the security guard if we would be ok parked in the disabled bay and explained and he said there was no problem.
It seems this is a private firm, Town and City car parks, who have given the fine, but I obviously do not want to pay it and googling suggests it's not enforceable and they probably won't chase it up.
AIBU not to pay it? Has anyone else had similar?