I still do not own a car yet, but I have been thinking about buying one soon. Since I live in the countryside and work a little with farming it would be practical for me to get a car that can be used off the road. A LandRover would fit my needs pretty good.

A website that sells Land Rovers is Guy Salmon Land Rover which have a big selection (over 300 in stock) of both new and approved used Land Rovers. They are selling all the current UK models from Land Rover in dealerships across the UK.
On the website you can browse their selection by model, what state the car is in (new, approved pre-owned or demonstrator vehicle) and the price range.

The used vehicles they are selling have been prepared and inspected by Guy Salmon Land Rover. You also get a warranty on the used cars. The warranty varies a bit by how old the car is.
There should not be any worries about the quality on the used vehicles.