Been looking at Estates myself, before concluding my commuter did not need to be an Estate.
Insignia Estate is shite, utter, utter shite in almost every way, it's far too small and terrible plastics all over the place. Out of more premium estates my thoughts:
Audi: Very poor space, but I very much liked the Interior
Jaguar: Awesome looking Estate, but space is poor.
BMW: Best of the bunch really for me in terms of useable boot space.
Not sure if BMW has the most 'litres' but for day to day use, appeared the most decent.
Volvo V70 is just dull, dull dull. Boring to look at, booooring inside and really just booring.
Merc: Came close to getting one of these at Car Giant, loads of examples for the money. Probably the biggest boot of all German brands and prob biggest one out there? Just disappointed with build, seats not very supportive and low amounts of tech. One £15k version I was looking at had no sat nav or bluetooth connectivity.
If I had to have an Estate and not a Mum Bus Zafira or Galaxy, I'd prob get a 5 series F10 shape, with Pro Nav and Sports Seats.