£15k budget, 30k pa - RRS / FFRR / something else?

[mondeoman]

Pondering on this for sometime later this year, with a 100 mile a day commute (mostly motorways, but they can and do grind to a halt at times, so no real opportunity for serious schlepping, although I do like to take advantage of any overtaking opportunities when they present themselves) and weekend dog carrying duty, would you go with one of the rangies, or is something else more, ermm, appropriate.

30mpg would be the target, so that means, for this size of wagon, that a diesel is the best option (or maybe an LPG conversion on a big petrol). Currently running an '03 A6 1.9tdi Avant; the boot is big enough for the pups and weekend trips to the tip, it gives 40mpg at best, if I stick to 60, substantially less if I get the chance to push on to 80+, but it really struggles with damp road junction traction, and that gets very frustrating.