As far as I know its only new 'structures' that need a new license - I think if its an already existing pit with a pipe going into a field somewhere(!?) you dont have to bring it upto a (the current) standard.
We all have off grid (presuming) cess pits here and most of the pipework has long been forgotten.
I have not been asked for the positions of any of my cess pits in current use,
- but I am however appling for a new toilet block for our campsite.
I am aware that any new s**t pits that are dug have to be of the current legislation. There are loopholes but who wants the stress?
Baz