The blooming Oled TVs have gone up in price Kezo. The 48 inch b4 is now £699 it was £499 a couple of months back ! That LG 2025 model UA7500 50 inch has good reviews John Lewis has it at £329 with 5 year warranty picture looks good on YouTube review
My honest thoughts are you can do better for that kind of money. The UA75, is a budget TV from LG in comparrison to your Samsung, which is more mid range albeit old now. You also got to remember, unless you are watching Youtube in 4k, it not really showing you much, yes 4k looks good on most TV’s and is the norm today anyway however, in day to day life how much 4k stuff do you watch, not alot, so you have got to look at how good the upscaling is from everyday SD & HD channels.
For £500+ your in the region of some mini LED TV’s, which would be seen as an upgrade to the next level, in the same way OLED would. Mini LED, have the advantage of being brighter (Nits) than WRGB OLED TV’s (LG C series for example), whils’t having very similar black levels to an OLED.
Compared to the number of TV manufacturers on the market, there is only a few scren manufacturers, whether thats OLED or LCD, so it’s worth bearing that in mind, because if you buy an LG or Samung TV, there’s a high chance they don’t make their screens, for example LG don’t make LCD panels but do OLED and, as one of the biggest OLED screen manufacturers, Sony, Panosonic, Hisense etc, use them in their own TV’s. Equally TCL makes many LCD screens fo Samsung. Apart from that where is everything else inside a TV made!
You worry about long guarantees, but don’t, a TV won’t break in 5yrs fact 99.999% of the time!
In my own view, you should be looking at Mini LED’s TV’s from Hisense & TLC. For one your not paying a couple hundred quid on a shiny name badge, remembering that TCL make screens for Samsung and LG don’t make LCD screens and the rest of the insides have come from Asia, mainly China anyway, even your iphone! Also look at the reviews of these mid range TV’s, thy are just as good if not better and these days are built in europe anyway.