I had mine outside, like you say, it grew great even though we had a lot of rain. The weather was so consistently dull that I decided to move it inside. I was afraid of root rot. I bought some grow lights and it began to grow like crazy. I am 4 weeks into flower and have several weeks to go. As I understand it, it would be late October before the day light/night ratio would be ok for the plants to flower. Again, I didn't want to take the chance and definately wanted to get some bud sooner rather than later. Are your's flowering?
What kind of seed do you have? I heard that northern lights is pretty good outside in the uk, but I don't know what it is like to smoke.