I think I'd take the Focus of that lot.
If you were allowed a 2.0 engine I'd be looking at the larger cars all the way, but I just can't see a 1.6 being particularly pleasant hauling around an enormous great Superb or 508.
I've driven a 1.6 HDi C5 and it was really lethargic.
I drove a 1.6 petrol Mk3 Focus Zetec last weekend and I was impressed. It was a Powershift automatic, but it didn't feel too slow and the TDCi is nearly a second quicker to 60 than the petrol. The spec is pretty good on the Zetec and it's a much more grown up car than the previous models in terms of comfort and refinement - many on here will say it's just a bog standard hatchback and of course it is, but the game has clearly moved on and the gap to the "premium" cars is ever shrinking. The friend who's car it is also has a 2008 Merc C180K Sport and he says the Focus is as smooth and comfortable to drive as that.