I was always led to believe that in any space that's designated to the provision of parking, there is a legal requirement to provide dedicated blue badge parking bays. Whereas the parent and child spaces, albeit a 'nice to have' are just that. They aren't subject to a legal requirement. All of the supermarkets Iocal to me that I use (as a wheelchair user), would actively encourage a BB holder to use a P&C bay if there are no BB spaces remaining.
Any private land owner can pretty much impose any parking conditions or stipulations he wishes, with the exception of the provision of BB spaces - they are a legal requirement and must be present. Hence, an unauthorised user can, in theory, be prosecuted for parking in one.
As to whether a BB holder could be penalised or ticketed for parking in a P&C space, well, in a privately owned and privately managed car park, then technically yes. However, I don't think any court in the country would side with the management company or landowner if provided with photographic evidence that a P&C space was the only usable space left for a wheelchair user.
There have been occasions when I have used a P&C space because one was available while all the BB spaces were full. But you do have to be prepared for the backlash that can result. Below is my most memorable confrontation - I was left genuinely speechless after this, and for a good many months after, I refrained from using P&C spaces, as I really did start to believe I had been very wrong.
I'd be interested to hear the views of mothers with babies in car seats and with prams:
I returned to my car one day after a short trip in my local Aldi, having had to park in a P&C space, to find a mum with her small baby standing by my car door. I asked her if she could just move along a bit so that I could open my car door wide enough to transfer into the driving seat. That's when all hell let loose. The woman had obviously been stewing the entire time I was in the store, as she accused me of so many things; being selfish, ignorant and entitled are the three that stuck in my mind. She said that she was sick to death of people waving their blue badges around, as if they gave them some kind of superpower that made them untouchable, and why my wheels were more important than her child's.. She then asked me if I had children, and when I said no, she laughed and said that would explain why I couldn't see the inconvenience I was causing and why I was oblivious to the potential danger I was putting her child in. She offered to let me watch her try and get her baby out of the car and her pram out of the boot whist parked in a normal space. I said I would do so by all means, but only if she sat in my wheelchair first, then transferred herself across into the car without using her legs, then folded up the wheelchair and hauled it across her shoulder to store it behind the passenger seat.
All this time, although she was quite forceful in her words, she didn't swear or raise her voice much. I think this is why I talked myself into believing I was the one being unreasonable. It took many lectures from friends and family, and many months before I was ever brave enough to use a P&C space again. Even now, it's only ever a last resort. I will drive round and round a car park to wait for a BB space rather than go through that again!