If I were you I'd try and hit up the Greek Isles by mid-September. September 31 is the last day of the tourist season, and although it sounds good to go when tourist season is over, it isn't because all the pubs close down and there is nothing to do on the Islands. September is the ideal time to go to Greece for both the weather and general experience of the amazing islands which is when I went a couple years ago. You should probably just go there before you go to England if you can work out the flight details - but don't go in August because you'll fry and be really uncomfortable.