Thanks again everyone. I can't believe my first ever thread generated two pages of useful info. I think I've worked out the source of my inflexibility. After a rugby injury 4 years ago I was unable to run or put excess pressure on my ankle, so no more rugby, jogging, squats, calf raises or ballet for me! So for the last 4 years in the gym I have been working upper body only. Neglect of the lower body has caused it to stiffen and now when I suddenly need flexibility (to simply put a board on my feet!!) it's just not there.
I've started a very rough stretching routine, but I have a physio appointment on Wednesday to discuss refining it properly for my needs. The increase in padding (which I keep telling myself is mostly muscle while others disagree) is due to the limited cardio I can do with a dodgy ankle. Although I can hack the alternatives when I do them - 3km swims, 50km bike rides etc - I simply don't do them often enough, and I've been looking for additional alternatives, which is one reason I've taken up kiting. At least my current health insurance will cover the physio, if not the kiting itself.