A friend of mine recommends a guy called DDP (he's an ex wrestler) who developed a yoga plan
He has videos on you tube, my friends lost about a stone and a half and says it down to that
Yoga is fantastic for posture and things like back pain, I think it'd be perfect for you. I used to have a lower back problem now and then when it'd almost seize up and I'd lose movement, haven't had it for years.
Pilate's concentrates on core strengthening, I did a lot after finding out I had a couple of Herniated discs in the Spine. Yoga is more of an all round activity and targets different areas around the body. Both very good
Pilates is fantastic, I just use videos from youtube, some great advice and workouts available for nothing.
I can recommend Coventry Runner, they film you running and pick the trainers that best suit your running style. Most comfortable trainers I've ever had, can run for miles and not had any injury problems since I've had them either. I would recommend getting some compression clothing as well, a lot of conflicting information on their effects but I feel better using them and feel that I recover quicker.