Thanks for your reply!

1) Well, I'm not doing any weight training anymore. I haven't done any since November 2010, where I stopped because I wasn't happy with my left shoulder mechanics. When I was training, I'd train 3 times a week, split between chest, back/shoulders, arms.... I found bench press was the only exercise I gained any strength in. But it was probably the exercise I concentrated on least - I was trying to get back and shoulder exercises right, but I found lat pulldown and shoulder press impossible on my left hand side. I kept telling myself that "it would sort itself out". I wasn't lifting heavy at all (I could barely shoulder press 5kg dumbbells).

4) I did do quite a lot of bowling in my early teens, but I was predominantly a batsman. The problem gets worse during inactivity, but paradoxically once it has started, any activity makes it worse. For example the one thing that was keeping me vaguely sane was going for a 45 minute walk every day. I've had to stop that in the last week because the pain in my hip, my calf, my foot and the tightness in my entire right shoulder, it just makes it impossible to walk and it just gets worse and worse. Instinctively I feel it may be related to extended periods sitting (e.g. at computer) and the poor posture that follows. The last couple of weeks I've developed a pretty unhealthy obsession with seating posture, trying to find the optimum way of sitting at a computer (e.g. lumbar support, trying various incline angles to keep spine in neutral position with minimal effort etc...). It couldn't be sciatica could it?