I’ve never had a problem with parking in a Parent and Child Bay using my Blue Badge when the Disabled Bays are full, which is usually the case at my nearest shops because there are only 2 Disabled Bays in the ‘level’ car park, but 6 Parent and Child Bays. To be fair, there are 6 Disabled Bays on the other side of the shops, side-on down the length of a really steep hill. It’s all ‘up hill’ getting back to your car with your shopping, naturally. 🙂