Currys is the worst place to go to look at TVs, I explain it briefly in the guide, but basically most of the TVs will be on max settings all round, plasmas aren't always because shops like Currys don't put as much effort into selling them (they're harder to sell because of the many myths surrounding the technology). Anyway, the PS3000 is dimmer than the rest of the LCDs, it's a feature of plasma TVs, but this isn't necessarily a bad thing, as I describe in te guide. You will turn the settings down from what they are in the shop and if you watch it in dimmer lighting then an LCD can be too bright, if you watch the TV in a very brightly lit room then an LCD will probably be better suited. The contrast on the plasmas will also look washed out due to the way the technology works and how it's effected by bright lights like those in Currys, it's all explained in the guide though.
As for the Samsung LED edgelit TV (it's not an LED backlit TV, that's in the 8500 and 9000 series, which might not come to the UK) Currys is the perfect place for it, and it will look amazing there. Basically they can produce very high brightness levels and very bright colours, but again, you will turn the settings down when you take it home and with the lower lighting levels the flaws with the technology will become more apparent. You will be more likely to get severe backlight bleed or clouding as that seems to be a serious issue on the Samsung models due to the edgelit technology, this is hidden in the bright lights in stores, but in lower lighting can be very clear. You could also suffer from the auto dimming technology, in lower lit conditions it can often become apparent and you get a flickering effect in dark areas, this can be particularly problematic with movies because this is not only when the light levels are often low, but there are black bars which makes the flickering most visible. Other than that though you will find that the LED edgelit TVs are very similar to the standard LCD TVs, viewing angles still suffer, motion problems still exist, but they do produce high brightness (which can be good or bad) and have a sharp image (no extra detail though).
You need to be very careful when comparing TVs in Currys though, the ones Currys want to sell will look the best