@TinyMystery sorry I forgot to answer the best and worst. I'll give my location away but I've nothing to hide. The best is Chester (aforementioned historic city) Zoo. They have scooters you can reserve if needed, some of the toilets are accessible changing places (as well as large and fitted with all the required bars etc, they have a hospital type bed, shower, and storage of all sorts of changing equipments and towels). My friend has a severely disabled son who is 13 and most of the time she has to change him on the floor of disabled toilets as there is nowhere else to do it. Places like this are invaluable. They have boats that take you around the Islands part of the zoo, and a wheelchair is able to go on it.
I have come across a few awful places, mainly individually owned/operated premises. One pub I went to I could get in and they had a disabled toilet, but when I opened the door it was full of mops, buckets, high chairs, stepladders, and coats to name a few. I got them to empty it out for me and found that the light didn't work. They gave me a torch to use. When I'd finished they piled everything back in there....
One restaurant I went to I rang first to check access as a friend was booking a hen do there. I explained that I was a full time wheelchair user and they said no problem. When I arrived there was a step and no ramp (the step was huge too), then to get into the place the doors were in a sort of chicane (sharp left, sharp right, sharp left), which made it tight. We got in eventually and we're seated at the front by the big windows, when I asked to use the toilet later I was told it was at the rear of the restaurant. The tables were too close together for me to get through.
Another restaurant had a small step to get in, but I knew that beforehand and arranged for people in my group to help. They assured me they had a disabled toilet. They did and it was pristine, raised toilet, bars, sink, emergency alarm etc, so what was the problem? The door wasn't wide enough to allow my chair to get in it!
I could go on...