These cars are great for over 100k miles, plenty of member in this region and still no issues except wear and tear.
As for the price it is really dependant on the year and mileage and engine model to decide as there is 3 different + 1 limited edition variations. 10k for 40,000 miles is good if its for talking sake a 54 plate, but may seem high for a 52 plate. It really is down to all of these factors tbh.
Mpg varies also, i get about 17mpg average others get 30mpg, its just dependant on your driving style.
If your worried about fuel and tax then it will put a dampener on buyin the zed. I bought knowing all these things and i dont grudge filling the car up with 100quid of fuel at a time as i enjoy every moment im in and out the car.
Fantastic cars and i have never looked back since i bought it. Its the first car i have ever bought and never thought about selling