I've just had a riding lesson - and 'Stella' - the instructor - has finally given me permission to place my lower leg where it feels best rather than where it is technically supposed to be. Oh my goodness - I can't tell you the difference it made! I can now canter properly and Phoebe even worked into some kind of shape! I have finally faced the fact that my legs will never be like Carl Hester's - no, no, no, mine are short and dumpy - not long and slender!!! (more's the pity).
At long long long last (after about 4 years of trying) I could finally control the speed of my horse in the canter. No more brown trousers for me!