I too am looking to replace my trusty old 1996 Disco with a pick up soon. Had the Disco years, it's like an old slipper and has served me well.
Have been slightly worried about some horror stories of some L200's having engine probs. the Isuzu Rodeo looks to be good, a pal has one and I've driven it quite a bit and it's nice. Another pal has a Toyota Hilux Invincible and that's nice too.
MPG wise the Disco only gives me around 25ish I would imagine, and have been feeding that for years so I'm used to the cost of fuel. I suppose there is good and bad in every motor, sometimes you get lucky, other times it turns out to be a Friday afternoon lemon!