I went to the opening of the CArdiff store about a month ago and they had a selection of LCD's and plasmas from Panasonic, Sony, Samsung and others, but not full ranges (I was looking for a Pana PX80 at the time and they weren't there).
However, I'm sure stock turns over fairly quickly but as for prices - can't really remember but I don't think they were anything special (except for the odd offer).
Personally, I'd stick with a decent indie AV shop for support or John Lewis for the warranty.