since this post I've had 4 weeks away from football and it seems to have improved. Instead of locking it now clicks through (relatively painlessly) the point of locking. Suggest to me that perhaps an inflamed tendon or ligament has perhaps recovered slightly?

I will be back to playing football again very soon and if the problem re-appears to the way it was I can safely say the training and playing is the cause. At that point I will certainly consider a private physio.

Thanks for your help.