http://www.empiredirect.co.uk/content/products/details/html/PAN-TH42PV500CAB.htm
I saw one of these running side-by-side with the previous SD version of this same plasma at a local Reliance shop in Derby. Both were running the same material - it was HD material at high bitrates showing a variety of scenes.
I was absolutely astonished at the improvement in IQ, which is also a lot to do with Panasonic's image quality and not only the fact that it was HD. If anyone wants to get a HDTV I strongly recommend getting a viewing of HD material on your chosen TV before you buy. This TV's IQ was the best I have ever seen.
Only downside is that the TV is out of stock everywhere and wont be in for about 3 weeks minimum.
I was about to buy the Samsung DLP 50" around XMAS time but I might have to reconsider now.