All good points @BigDave although, regarding premium brands, it’s worth remembering that their residual values are often better so it doesn’t always follow that AP’s will be significantly higher. Furthermore, many BMW dealers would often provide £500 discounts on advertised AP’s.
We changed our Motability car last year and our £40k BMW X1 cost us just £2,249, comprising a very reasonable £2,749 AP less a £500 discount from the dealership. That was no more, and in some cases less, than comparable cars from the mid-market manufacturers at that time.