Ah a topic close to my heart! I'm 6ft 8"
Mondeo mk3 = perfect for even my size
Mondeo mk2 = dunno
Vectra 04 onwards = Similar to mondeo mk3, perfect size wise.
Ford Focus (98-05) = Also great for me on manual or auto which i was kind of surprised at.
Gen 6 Toyota Celica was fine actually on an auto.
Gen 7 Toyota Celica = can't fit in at all weirdly, they made it smaller!
Honda Accord 98-03 seems great on the auto, not convinced on the manual.
Honda Accord 03+ i could def fit in 'ok' with a manual or auto.
BMW e39 5-series is great
BMW e38 7-series even more so, best roomwise i've come across. Tbh i'd be quietly confident i'd be ok in this if i was 7ft 8, nevermind 6ft 8.
BMW e46 3-series i've recently been told should be ok but when i tried it wasn't very pleasant
I recently had this same dilema and decided it wasn't the right time (with taxation laws kicking in) to go for something too adventurous. I opt'd for an 00 reg Honda Accord exec automatic 2.0 and i've been really pleased with it so far, very easy to live with day to day and easily enough room. 40mpg on a run, maybe 28mpg combined.