I have Virgin TV so that has a few HD channels.
The Virgin Tivo box makes a pretty good job of upscaling the SD channels (although the older Virgin HD seemed slightly better), but it is still broadcast HD and not ‘Full HD’, so still subject to upscaling artifacts which you will see if the screen is too large for your viewing distance.
So I would still think seriously about getting something that size.
Go into a store and get them to show some Freeview SD to see what bad artifacts look like, and then get them to show BBC HD to see how mediocre that is compared to the demonstration bluray they are probably using.
Plus I wouldn’t personally get an LG, nor a Samsung as I think their picture processing is pants.