LCD is a liquid and plasma is gas( very simplified)s. You are unlikely to find a Plasma of less than 37".
However I set out to buy a 37" LCD and ended up buying a 37" Plasma. In terms of viewing LCDs have distortion of picture from the sides whereas Plasmas generally give a much brighter picture . They are, in theory though, subject to burn areas. As generalisation for picures of 37" and under - go for LCD and for above that go for Plasma. Hope this helps. What really persuaded me in the end was the 5 year warranty I got and as Stevie has suggested John Lewis do seem to offering a good deal.