Just to add my bit to this.
I have the same issue.
HD content on Netlix has micro stutters and is unwatchable.
I then rented a HD movie from TalkTalk amd it has the same issue.
I changed to a BT Humax box because my TT Huawei box is really slow and sure enough, same micro stutters on Netflix and movie rental HD content.
I have been saying these boxes need 60hz.
The sad part is, when TT TV (Youview) was launched the box was 60hz.
But people asked to have their box changed to 50hz (God knows why with modern TV's) and TT did this remotely..
Now all boxes default to 60hz.
People complained about this on the Youview forum ages ago and it got buried and ignored.
My PS3 outputs at 60hz and there is no micro stuttering caused by frame rate.
You get the same issue if you take NTSC material and badly convert it to Pal. The very same micro stutter.
I now use my PS3 for Netflix. And will tent movies in SD 