Originally Posted by chevvron
It WAS enshrined in CAP 670 rather than just being 'a sort of policy'...
No it wasn't, in part because of differences in philosophy applied between two parts of the CAA. Whatever might have gone into CAP670, and there may well have been references to the level of service from what I recall, it was only a small part of what I have in mind as the 'sort of policy'.
I suspect what you are referring to is the drive at one point to 'upgrade' a number of busy aerodromes which offered an A/G communication service to an Aerodrome FIS. And that opens another can of worms because at one point there was little apparent difference between A/G and AFIS (especially from the pilot's point of view) compounded by the CAA starting to make the UK AFIS service much like aerodrome control from the apron to the holding point; yet another source of confusion to many! And, if I'm not mistaken, chevvron, you had some input to the discussions which led to those decisions.