I recall many years ago seeing the ticket office clerk at Princes Risborough close the booking office for a few minutes in order to cross the footbridge to the down platform and place a ramp against a train that was shortly due to arrive from which a passenger using a wheelchair was expected to alight. it's one way to deal with that issue, though at the expense of an open booking office for a few minutes.
As well as Little Kimble and Monks Risborough, mentioned in earlier posts, Saunderton and Denham Golf Club were unstaffed, and Chiltern presumably has an arrangement for wheelchair passenger at those places.
I've put two sections of the quote in bold, because they're activities to which the phrase "more honoured in the breach than the observance" could well be applied. If, on late at night trains on Friday or Saturday, the guard doesn't patrol at all, I hardly blame him or her, because I wouldn't like to have to do it.
V