UK Cortana seems to be working fine for me. I just find it hilarious and quite weird when the robotic voice does the Halo references, some jokes and impressions! Maybe the British Lady needs to do some more recording?
My Lumia 520's battery life is pretty much the same or possibly better than it was on WP8, again it could be just the apps aren't optimised for 8.1 or that people are playing around with their phones a lot more.