Toby - a very good question indeed.
Due to historical and legacy reasons Societies have been mostly autonomous, or part of the County Union. More recently many Societies have set up written constitutions and operating pronciples with an annual operating plan.
That would have the formal complaints procedure outlined.
Societies tend to have a catch-all clause in their constitution (similar to RFU's 5.12 bringing game into disrepute), of bringing the Society into disrepute.
In many cases Societies still are invitation to join oranisations, it is not open membership, you have to be nominated / recommended and you are not 'dismissed' but your membership is withdrawn, not renewed etc. Very much a historical legacy of 1920s/30s but also makes the Committee less accountable and avoids any employment appeal type discussions.
Since the mid 1990s and setting up of RFU Refs Department there are 'dotted line' reports from Societies to
a) Governance - RFU Council through County CB or Refs own CB (RFRU)
b) Structure, referee development, performance, recruitment & retention - RFU Refs Department through Regional Referee Development Managers, who in return support Societies with organisational and training materials.
c) Referee Development - Federations, Groups and National Panel / Refs Dept
d) Discipline - County CB & RFU
Do remember that we are all vounteers, except the paid full & part time RFU staff, so the RFU is not a push down demand management structure but more of a supportive resource.