OK - Requirements are for a 4X4, which will mostly be driven on road, be reliable and economical and cost between £6-8k:
Nissan 2.2 Diesel X-Trail is ideal, but costs at least £10k - If you can stretch to that much, close your eyes and go for it.
Of the rest:
Subaru Forrester - Excellent car. Very comfortable, capable, stylish, and very very reliable. Downside in the petrol costs. You'll struggle to better 22mpg from the 2.5 litre engine.
Toyota RAV4 - another good car (I bought one for my sis-in-law), available in the price range, economical and reliable. But... Not great off-road, interior a bit plasticy for my tastes.
Older, Bigger cars:
Mitsubushi Shogun/Pajero (Pajero is Japanese market import): Very good, capable, rugged, economical and reliable. You should be able to get a later 2.8 turbo diesel - but, they are big, and heavy, which usually means bigger bills - Tyres, fuel etc.
Jeep Grand Cherokee: older shape model for this price. Good image, OK off road, course diesel available to better economy, reliability so so.
Oddball:
Toyota Hilux Surf: Mostly available as an import. You should be able to get a post '96 3.0 turbodiesel. Good power, very reliable, very rugged and good offroad 28ish mpg, and I think looks great if you can find one without the two-tone paint option.
My Choice? If I could stretch the budget, Nissan X-Trail. If not, Subaru Forrester.