AFAIK all Samsung and LG TVs support 4:4:4 (a color mode you need for text to be displayed legibly) and have good input lag in PC Mode.
For TV use you want post-processing ON and for games OFF, if input lag is important. The extent and quality of post-processing is one of the differences between more and less expensive models, sometimes expressed with a marketing pseudo-benchmark such as PQI (higher is theoretically better)
When used as a monitor the typical LCD TV suffers from backlight flickering which annoys and/or fatigues some users – others don’t perceive it, and it’s not generally a problem when used as TV.
All decent TVs do upscaling, and much better than monitors for sure, but you’re not likely to be super happy if you intend to play games that have small-ish text and/or elements in their UI, such as say, a strategy game like Civ.
If indeed your card cannot output a UHD signal (are you absolutely sure?) desktop use might also become a problem, likely forcing you to increase UI scaling.
Rtings is a good resource to select a TV, however keep in mind model codes and availability might not match exactly what is available in the UK.
Remember different sizes of the “same” model can have different panels. Speaking in general:
- IPS is better suited to wide rooms where viewing angles are important, with multiple people watching the TV at the same time. Has worse contrast and dark room performance suffers.
- VA has less wide viewing angles, but makes up for it with deeper blacks and higher contrast.
I’d recommend you start here for selecting a TV size that fits your needs:
Also keep in mind that, if driven at native resolution (UHD not 1080), 40" screens have about the same pixel density as 27" 1440 screens, which is roughly 20% higher than your average 24" 1080 monitor.
'fraid you will have a hard time finding a decent TV on the market that is not Smart anymore, though.
This article offers a number of solid recommendations for a Gaming oriented 4k TV, remember if you’re not super strict about the gaming requirements, you can expand your scope a little – in fact some of these recommendations already keep that into consideration.