I'm a huge advocate of the KS range, I personally have a 55" KS7000 and its fantastic. There are some issues with OLED, say with clipping on HDR content. The LG OLEDs did have lag issues but I believe that's been resolved now (US had a firmware update to address it, Europe was waiting for it last time I heard)...
A big part of recommending the KS range though is price, it's is insanely good value where I think OLED still need another year until it's really worth that kind of outlay. At the moment the Samsung KS vs an LG OLED trade blows, each have positives. OLED will eventually win out though. The current OLEDs are fantastic but as a new consumer tech it's no where near maturity so each year will bring gains which could tempt an upgrade.
Samsungs QLED range is a bit of a con, it's not proper Quantum Dot.. They're still fundermentally LCD panels.
It's a difficult time at the moment, spending £3k on a TV... All the improvements that are coming with new formats, also the HDMI spec in 2.1... You really want to wait until end of 2018 if you're spending that kind of money... Its personally what I'm doing, will likely make the move to OLED early 2019, providing the improvements expected materlise.
I'd advise waiting a year and instead spending 1k on a decent 55"... If you absolutely feel the need to spend £3k, go for OLED. You may aswell with that budget.