I'm pretty sure that the stutter I saw was down to tuning issues. When I set up the tuner in 7MC it came back with a large number of signals for the Freeview stations as I live in an area where 2 transmitters can be picked up. I manually selected 770MHz for the HD channels as listed by the UKFREETV website for Midhurst, but when I went back to the detected 770.167MHz it stopped the stutter - or it appears so. Watched Silk on BBC 1 HD last night and didn't notice any.Very little differene between Hd5450 and HD6450 ??
Anyway, it looks like my HD5450 doesn't need upgrading just yet!