My local Currys store doesnt carry the high end Panasonic plasmas any more, as they seem to be much keener to push the latest consumer want, the "LED TV". Only LED backlit I'd consider would be a full array one like Philips make, not one of these fancy thin edge lit jobbies that look good, but all have patchy pictures. The technology is getting better, but probably won't be fully there before OLED is with us (and more affordable hopefully). There's a big barney going on in that arena, too, with Samsung and LG both suing each other over the tech, just like Apple, Samsung, HTC etc in the mobile phone/tablet world!
If you can get to a proper Panasonic dealer with a full range in stock, you'll see where the extra money goes and it's mostly on the chassis. The GT and VT ranges are lovely to behold, whereas the ST looks rather more plasticky. The VT is stupendously thin for a plasma, but the price is wince-inducing.
edit: just recalled that the VT doesn't come in 42" flavour anymore, so even if it was more affordable it won't fit...