[Q] Advice needed: LG G3 D856 vs D858 and UK LTE Coverage topic

Hi all. I'm looking to buy an LG G3 Dual LTE but being in the UK my understanding is that only the D856 would offer better LTE experience considering it supports the FDD 800m Band (FDD: B1(2100), B3(1800), B7(2600), B8(900), B20(800), unlike the D858 which supports 2100(B1)/1800(B3)/2600(B7)MHz .
I've been looking for this model for days now but all I can find is the D858 which seem to be widely available.

What are people experiences with the D858 in the UK? Has anyone managed to buy a D856 from anywhere?

The SIM I will be using for LTE is a Three SIM

Alternatively can anyone recommend a good alternative to this phone? (Not S5 or M8 though)

Thanks in advance