yay! another UK'er on TE! Don't worry so much about the speed. It'll come. I started off doing about 10mph and I live in the flatlands of Essex with no hills and have been commuting by bike all my life. I'm now up to 13mph on long rides, but that's after over a year of serious bike training. What got my speeds up was just lots and lots of bike-time, and some focus on pedalling technique to make the most of going clip-less. And I started doing some interval training too which helped. But it all takes time. And in my opinion, as long as you're having fun the rest will come by itself eventually.