wow kipper, you just beat me to posting about my life
I too live in UK, have a 18 month old Hitatchi 42CP3000 (i *think*). I watch 90% of everything though a DSUB cable from my HTPC. Yes im a US TV fanatic, I *cant wait* for TV to show here. (i guess you know what thats a euphamisim for...). BTW I do wait for films.
Anyway, through NTL, channels like E4, Sky1/Mix and Channel5 (!), are all crystal clear. BBC can be fairly bad, and ITV is middling. NTL is cable, so signal strength isnt really a concern. Its the OTHER end of the line you should worry about. In order to save money, tv companies will reduce the bandwidth of their channels, which degrades the quality. This isnt a problem on smaller screens as you cant see the flaws, but big digital panels tend to suffer.
Messing with the constrast/brightness/sharpness can help. You might not get quite so vibrant colours, but the image problems are noticably less.
One good thing to note: it would seem that TV companies are realising more people are getting bigger TVs. Le Tour de France on ITV2 this year was a marked improvement over last year. Not crystal quality, but definitely not the blocky POS from last year.
And for DVDs and *real* HD rips, its awesome!