Chevvron is correct. JSP 318A was superseded by JSP 552, which as been replaced by MMATM (Military Manual of Air Traffic Management).
NorthSouth's link no longer works as the government have changed their web addresses
, but the document can be found here:
http://www.maa.mod.uk/linkedfiles/regulation/mmatm.pdf
Chapter 24 is the area to start looking, specifically pages 212 and 218-224.
I hope this helps.
MM