Night and day difference between late Mk2 and early Mk3 Mondeo diesels. Had/have both; comfort, ride, handling, refinement and any other benchmark you care to name, the Mk3 wins hands down.
MK2 on an S with the 89hp Endura engine, only got 37.7mpg over the 10k miles I had it (100 miles motorway commute each day) Worst car I ever owned.
Mk3 on a Y with the 115hp Duratorq engine, so far 43.71mpg over the 48k miles I’ve had it. Same commute.
Estates by the way.
I’d go for an early B5 Passat, 110hp if you can find one. Better than both the above on economy although service parts are generally more expensive. If the cam belt’s been changed don’t worry about mileage, sold mine with 175k, friend has a 20v with over 230K on it.