I would tempted to go along the lines of something like a BMW 320 diesel 60+mpg but be sure to check service history especially to see if it's had a new turbo as they are quite prone to blowing them, also the bottom crankshaft pulleys can become worn and rattle about which sounds like a big end. Vws/audisand seats etc are ok ish only the newer models the oil pump runs off a silly little hexagonal rod which are again prone to ware causing low oil pressure resulting in 1stly turbo failure then the bottom end. Another thing to watch out for is the injectors if these fail your looking at the best part of 2k, Also I wouldn't be going for something that has been remapped either as it's more strain on the engine.
The newer peugeots are quite reasonable too these days my dad has one sure it's a 307 and think it's a 1600cc hdi that's awesome on fuel but I suppose the older you get the more respectably you drive things thus saving fuel lol
No doubt which ever car you think about there'll be loads of pros and cons you'll just have to way them up and ask advice