Black cabs are more accessible by default, but I'd assume if I called ahead for any taxi I'd need to let them know of any special needs, the same as if I needed to let them know I wanted a taxi for 7 people?

Shouldn't there be an area for adding special requests such as accessibility? You filter to the vehicles that are able and willing to take this passenger's money.

I can only assume that, as contracted drivers, they have to worry about scratches that may be caused by loading and unloading wheelchairs? Am I overlooking some kind of personal discrimination expecting people to be better?