Just no, no and more no.
Given that recent (2011 onwards) 'smart' tvs and devices: bluray/dvd players, have been losing their 'smart' apps already and the only solution is to buy a new device because the manufacturers, Hello Sony, Panasonic, Samsung + others, are no longer supporting them or willing to update the firmware, I can't think of a single sane reason to buy one of these.
Ignoring the ridiculous 'please wait while we update' before you can even see a picture situation, slapping the innards of a tablet at the heart of a TV is just a recipe for disaster. Even if the OS is updated from Google/FireFox, not the TV manufacturer, I can dream, what are the chances of the apps still working in 2-3 years on the version of the OS which will run on that hardware? Looking at the tablet market, I'd say not great.
For £1,800 if UHD is so important, just buy a 50" screen for <£1,000, a Humax YouView/FreeSat+ recorder, whatever streaming box suits FireTV, NowTV, Roku etc, spend the change on either more goodies, lots of beer or a holiday. I'm all for convergence, but only when it's possible to swap out or replace the broken and unsupported bits easily.
I guess I'm going to need to hoard even more cash and buy from the professional display panel market when the time comes to replace my screen.