Need Help with NHS stance on exercise prescription

Hi,
I am writing my dis on exercise sheets vs. face to face tuition. But i cannot seem to find much on the NHS's stance about perscription of exercise or how the NHS views this in relation to cost cutting and etc.

I figured there would be a fair amount seeing as it is a money saving measure and people have mentioned to me terms like 'any qualified person' being able to perform tasks that are not necessarily within their field of expertees.

Can anyone recommend any readin or relavent journals ?