There's no chance of anything more than 30 out of a proper 900. I have a single carb n/a and it struggles to get 30.
I personally like simplicity so some of these suggestions are slightly short of your mpg target and they're all a bit boring, but this is what I looked at before getting mine... (and yes, I like French cars)
Synergie 1.9TD (I bought one) - most practical car ever. Cavernous rear, because all the seats come out. Sliding doors both sides. Super reliable, 45mpg. I paid £750 and it has needed very little maintenance for two years (150k miles on it). I would buy another in a heartbeat!
Synergie HDi (you probably want the 110) - as above, a bit more economical/faster/refined, but fussier engine and more expensive to buy, you'll still find one for around £1k though.
If you want leftfield... BX estate, ye venerable 1.9TD lump or the 1.7 is good too. Around 50mpg, loads of room, magic carpet ride and great handling, masses of spares availability, good owners' club forum. (I have a BX 16v and I'm sure I can point you at a good estate)
Citroen C5 estate or 406 estate HDi.
405 estate 1.9TD.
Skoda Felicia estate. Agricultural but 60mpg.
Golf 1.9TD estate , as above but even more biblical mpg (friend had one that hovered around 75mpg).
Multipla you know about.
Land Rover 110 2.5TD/200tdi will get you around 30mpg, not as much room as you'd think in the back though, but lots of fun and will last forever but you need to maintain it. 300tdi is too complicated IMO. V8s with LPG conversions are around but you'll be lucky to see an equivalent 25mpg with those! Discos are good but really don't have much room in, Range Rovers... old one = money pit, P38 = too complicated, anything after that = too expensive. But of course you'll be bloody lucky to get anything apart from a very tired P38 for under a grand anyway.
(Certainly on any in this price range)
