I cannot speak in generalities about the UK but generally in the US wheelchairs are readily available. Simply because many times patients are discharged after surgery and aren’t capable of walking considerable distances afterwards.
Sometimes, I have found when you are polite and ask simple questions it gives people the ability to avoid answering directly and equivocate!
I have observed when people instead assertively make a direct statement/ request/demand they are amazingly less likely to have their needs denied.
My mother case in point made her needs nearly undeniable. So assertive/aggressive that it assumed there was no reasonable way a person could deny her. And she seldom was!
I simply found this approach rude and assuming.
Which was exactly why she did this particular behavior.