Your mileage is extremely low, far to low to financially justify a Motability vehicle.
This is a very important point which a lot of people overlook. You are doing a little over 3000 miles a year, does this warrant a new car with £1000 ish AP every 3-5 years? I think you are right to consider purchasing, but I’d keep it longer than 3 years. My last privately owned car was 15 years old and only ever needed tyres and brakes.
Using the poster figure a 3 year lease with 3000 miles per year works out at £1.02 per mile plus petrol cost?
Using £71 per week + £500 = £1.29 per mile ?
Unfortunately I have suffered a brain injury and occasionally I get confused and often say the wrong thing.