I'm 6'6" and have a 05 Opel Vectra and there is plenty of headroom. Legspace is adequate to good (I have very long legs). Seat isn't hight-adjustable in my model, not sure it it's an optional extra. However, there is an adjustable lower back support built into the driver seat, which I find great. Overall I 'm very happy with the comfort of the car.
Would agree that the Mondeo is not all that suitable for tall people. Also recently sat in the Volvo V50 and S40, and the legroom wasn't great at all.
My wife has the new Corsa, and I was amazed how much head space it has. I wouldn't drive for long distances, but it's great for short trips.