In my days as a trade plater I frequently had to collect ex-Motability cars to take to auction (either at the end of their lease periods or because the driver was no longer able to use the vehicle, through illness, infirmity or death).
The vast majority had very low mileages on them. (In one case a car had just 38 miles on the clock as its driver had found, just after accepting the vehicle, that he'd only got a short time left to live and he wanted to sort out his affairs quickly. He even let me keep everything that was in the car, such a very expensive waxed jacket, as he said that he'd got no further use for any of it).
Most vehicles had usually done no more than about 3000 miles per year (with some having done considerably less) and had been cared for extremely well. The only vehicles with much higher mileage seemed to be those where the person obtaining the car through the Motability scheme almost certainly hadn't been the person actually driving it.
For example, I went to collect a Motability car from an elderly gentleman's home in Southend but, when I got there, he had to phone his grandson to bring it round. The grandson's driving style, upon his arrival, appeared to suggest that he was one of the 'boy racers' who congregate on Southend sea front. The whole of the back seat area was covered in hundreds (NO exaggeration, I assure you!) of empty fast food containers and turning on the radio nearly deafened me, as it was set at the highest volume level possible, with the bass turned full up and all of the presets set to heavy rock stations. Somehow or other, I very much doubt that it was the elderly Motability customer that had actually been driving it!
So (as long as you avoid the vehicles that are rare exceptions to the norm, such as that one from Southend) any ex-Motability vehicle is likely to have a genuine low mileage and to have been well maintained. However the motoring trade are fully aware of that, so ex-Motability vehicles generally achieve high prices at auction (meaning that the dealers whop buy them will then charge quite high prices to their own customers).