Hi Mok79, Andy98765 has given some superb advice, you honestly should heed it and try a few things before swapping the screen. The PX60 should be giving fantastic PQ, mine and a thousand others are i can assure you.
Before you blame the screen look at the facts-
1. You're feeding the screen with possibly the worst transmission possible...NTL. As has been mentioned it's on a par with analogue, not good.
I too changed from NTL to Sky+, and then Sky HD
I find this source simply superb on the PX60. (Maybe a little drastic for you to change to Sky HD but with NTL being such a poor source will it not be just as bad on the Samsung?).
2. You have no aeriel?? And yet the PX60 gives a great picture on most channels via its inbuilt freeview.
3. Although we have little detail on the Sony one might assume it's not a high end £600-£800 player? Perhaps it's a non-upscaling cheaper model from Curry's etc? Couple that with a scart connection (not that much higher up the scale than composite) and yet again you're falling short when it comes to source and connections.
If it has component connections get yourself a set of leads similar to this-
http://www.hificables.co.uk/ProductDetails/mcs/productID/10886/groupID/709/categoryID/2384/
If not you could consider upgrading to an upscaling player with either component or HDMI connections?
To be truethful i think your barking up the wrong tree somewhat. The PX60 is a fine screen and the PQ should be superb given good feeds. Remember as with any screen......crap in crap out and the 42" Panny is gonna show all the flaws from inferior feeds, as you're finding out.
Also unless you're visiting a specialist AV dealer take no notice of what you see in the high street! Many have reported the PQ of their screen looks awesome compared to that displayed in the shop. And in your case it works the other way round as well! The Samsung may well look great in the shop but get it home and take the HD feed out of the equation and you'll be back to square one.