I got my G3 today, I'm not in UK but also experienced the low signal issue, having 2-3 bars on my entire apartment, upgraded from an Optimus G, and signal from it never goes down from full. Did a little experiment, tried changing Network Mode on settings, it was on GSM / HSPA /LTE auto by default, i switched it to GSM / HSPA auto. Instantly after doing that, My G3's signal improved. From 2-3 bars to FULL. I don't know why signal is low if the default network mode (GSM / HSPA /LTE auto) is chosen, hope LG does something about it whenever a firmware update comes.