Hi kali, my dad spent many years in the motor trade so is very picky when it comes to buying cars. My mum's last three cars have all been low mileage Japanese ex-motability from car auctions (always the cheapest way of buying). It is possible to get something genuine privately but it's difficult and ideally you need to know the seller. He won't touch anything French or Italian and considers German overpriced and expensive on parts and servicing. So that basically leaves Japanese and some others to consider which are well built, reliable and good value. He considers anything over 50-60k miles high mileage. But you have to consider he has a motor trade mentality.
I wouldn't consider going for a really high mileage 4x4 cos they can work harder and take more punishment than other cars. He actually uses his off road at times. Apart from a few parts and scrapes, most done by other drivers his is going just like it did when he bought it. It's done nearly 100k miles. He sold Nissan's for a long time and rates X-Trails very highly, he nearly bought one. But bear in mind the bigger the car usually the bigger costs. I wouldn't go for a Range Rover they are so nasty inside and very big and chunky on the outside. Then again, if you can find a car that's clean on the outside it's probably good engine wise. As always whatever you buy make sure it has history, check for signs of damage, different shades of paint on panels and paint on rubbers and seals indicating it's been painted. People selling cars lie. Stay away from anything that is starting to rust. Beware of shiny tyres and shiny steering wheels. Most of the independent dealers clean the hell out of their cars when they put them in auctions, if they look too good they probably are. Shiny steering wheels means lots of miles and use whatever the clock says. Check under any seat covers and the boot under the spare wheel for rust. Stay away from cars making any funny noises. It's a minefield basically. A different tyre on each wheel can sometimes indicate not the best cared for car. There are lots of things you can look for.
I would recommend a T-Cut and gloss polish of whatever you're selling. It will kill your arms but put extra money into your car. Use masking tape and/or newspaper over any mouldings/trims and rubbers once you get polish on these bits it is very difficult to remove. You can use black shoe polish on any rubber bumpers or black plastic trims. If you use 'Back to Black' it's not that great and you probably have to go over and over the same bits. It wears off quickly too. I put new brake pads on mine before I sold it, don't sell someone a potentially dangerous car.
You could try here if it's not too far:
http://www.brightwells.com/Vehicles/4x4/Default.aspx