I mean its difficult, because the obvious choice is the 4K TV, but much like HD 1080p/720p its a long way off from having it as a broadcast norm, we are hardly in a HD broadcast environment yet, but if you watch blu-ray and can upgrade your player so that it upscales to 4K then you will be very happy indeed,
also go into store and have a look, some of the 4K's I have seen look a little wishy washy to me,
I am about to buy a new TV as well, and put a list together of what I need,
wifi
smart TV(Netflix etc)
min 42 inch
LED
wall mountable
lightweight
you get the drift, this way I can tick of the requirements and achieve the lowest price.
I am going to go with this one, which is similar to your first suggestion, only a 42 inch, £50 more from john lewis, but with a 5 years warranty, which is rock solid.
http://www.johnlewis.com/lg-42ub820v...ew-hd/p1653110