If you fancy a bit retro... a Volvo 240 Estate - yes long enough to sleep in, ridiculously cheap & reliable (Mine was £250), very comfy. Economy is bad (Maybe 25 on long runs for 2.3 petrol) but depends on mileage against purchase price...?
Probably you hate that one (most people do).
Can you sleep in an Aerodeck? Too old?
If you don't think Mondeo estate's are too dull they're good on price v. reliability.
Maybe also too sensible(?) Skoda Octavia Estate's can be stoating bargains vs a passat (I Guess a golf underneath, mind

More character? I'd look at old Merc estates (Preferably not pre '95-'04ish when the accountants got involved).
Or - again a bit old and economy not the best - an E30 (or other) 3 Series estate.
The other two I'd personally consider, which I'd guess (Open to argument) would be reasonably reliable although maybe not the cheapest on fuel would be the Subaru Legacy Estate (Petrol only if cheap) or Mitsubishi Galant?
Actually, I typed this assuming a budget of £1k, and just saw is more. Still. Some relevant.
My .02