Try Afghani or a Northern Lights strain such as Northern Lights pure indica or Oasis which is Northern Lights #9 or #2 (can't remember which). I live in the UK too and I've grown both of the above strains. They survived freezing weather, rain and everything and I still got some pretty good buds off them, especially the Afghani. I did start them off in a little greenhouse though (you know the tiny plastic ones you get from Argos or wherever.
Look for an indica dominant strain with an early finishing time; avoid sativa strains at all costs, there's no way they'll mature in this country.