Hey, welcome mate! I'm in Reading, ('bout 30 mins West of London for those who dont know).
I have to agree that the weekends on the sites accepting US players are noticably easier than through the week. The two downsides of waiting till very late UK time to play the US donks are 1) You end up tired, and 2) The hardcore from Scandinavia and Europe are around, and they are just as tough (perhaps even more so) than their American hardcore equivalents.
In my personal experience, of course.