Assuming I can find a PVR with a USB port can I transfer movies to a TV with a USB facility (latest Sony's)? If so, what amount of memory would be required for say a 2 hour movie on an SD card that slots into the USB connector?
You can.
But why an SD card? why not a USB stick?
Memory depends on video format.
All depends on quality of video.
DVD quality takes around 4.5GB for 2 hours.
VCD quality is around 700MB for 2 hours.