If you're going to buy one in the UK, get an ex-military 110.(3500 quid upwards from a dealer with a warranty) (Preferably ex-Air Force as they are used more gently than Commando and Army trucks). They are already set up with extras like heavy duty suspension, jerry can lockers, XCL tyres and so on, and some have snorkels and winterising gear. Theyve also been meticulously serviced since new and many are also Waxoyled. However if you get an ex-Commando one, check it's not one of the Beach Assault or Wading versions as they often have heavy seawater corrosion, though that's not always so.
They come with the 2.5 diesel engine (nonturbo) which is low in power but extremely reliable and tough. With care it will return 70mph on motorways and about 22mpg and Ive had it climbing big Saharan dunes with no dramas. Perfect overland truck - indestructible and extremely reliable

I paid 7000 sterling for my ex-Commando winterised truck five years ago from the Defender Centre in Stourbridge and it's been simply fantastic.

After fitting (and then overlanding) a fold-out double bed and a single bunk above it (perfectly ok, a bit of a tight squeeze) I am now running a boarded-out back with a false floor with storage lockers underneath and living space above. Ive just put a roof tent on as well, which is a great bit of kit. Wagon will be at the Billing Land Rover show with two other overlanders in July if you are in the UK then.

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'91 LR 110 Def/Disco hybrid "Elsa"
Bring me the horizon....