Yes, nice to agree.
The Governance of WMUK is far from settled AFAIK. A very large group
(hundreds or thousands) cannot have a single voice with some
hierarchical or other structures.
The Governance is pretty much determined by the Companies Act 2006,
the Memorandum of Association and the Articles of Association. There
are members who elect a board at the AGM and the board runs the
charity. The members have certain additional powers which can be
exercised in writing, at AGMs or at EGMs. "Member" is this context
means "guarantor member".
The part that isn't settled yet is membership fees and what forms of
membership we'll have (if any) in addition to membership of the
company proper, but whatever is decided, they won't get a vote at
AGMs.
Having 100s or over 1000s of members shouldn't be a problem - most
will probably vote by proxy at the AGM. There are public companies
with 10s or even 100s of thousands of shareholders that manage just
fine, the vast majority just fill out a proxy statement that is sent
to them in the post and never go near the actual meeting.