Only if you got the mpg calcs wrong. 
I've driven plenty of fully loaded hatches and estates at 70 (ain't nobody got time for 60 ffs
) and nothing got over 55mpg, well except the 106 but you can't get much in those lol. Even the Golf's would only do 60+ empty, soon as they were filled that dropped to about 50. Full Vectra would only do 40!! Granted an empty estate probably will do 55, I'd go for a PD Audi if that was the case, but why buy an estate if it's not used?
I've driven plenty of fully loaded hatches and estates at 70 (ain't nobody got time for 60 ffs
) and nothing got over 55mpg, well except the 106 but you can't get much in those lol. Even the Golf's would only do 60+ empty, soon as they were filled that dropped to about 50. Full Vectra would only do 40!! Granted an empty estate probably will do 55, I'd go for a PD Audi if that was the case, but why buy an estate if it's not used?