Pro-Tip for anyone who wants to get in shape for the coming warmer season! How about checking out some of the (very good!) Yoga and fitness videos that you can find on Youtube?
This is a great way to get in shape without you even having to leave your house! Just fire up a video and follow the steps. There are plenty of very good fitness courses on Youtube if you look around.
At Hackney Gym in East London you can find more classes for Health and Fitness and they also have motivated and qualified trainers to help you get started! Visiting a good gym is a also a great way to meet and socialize with like-minded folks! Personally I think that going to a gym where you can do your exercises with many friendly people is a lot of fun and super-motivating to get in shape!