Some good advice on here, fully agree with the most important factor being well maintained rather than just mileage.
Also consider all the new Clean Air Zone charges, we’ve just been stung for a £189 for driving into Bristol in December, didn’t know about the charge and the penalty letter was lost in the post.
Turns out you need a Euro 6 diesel to be compliant currently or a Euro 4,5, or 6 Petrol.
Check out what the city near you requires as that could have a bearing on choice