How much detail do you really want ?
Apologies in advance to anyone who actually reads this.
I think we are probably all agreed (?) that ACME is a distinct group from WC but that there will be a great deal of crossover between the two with many ACME members also being members of WC. That is probably a crucial distinction; you can be a member of one without being a member of the other.
I don't know a lot about WC but I do know that it is an affiliated group of Cycling UK. This gives it access to some third party insurance cover subject only to compliance with certain Cycling UK rules. As an aside, Chelmsford CTC is an informal group of Cycling UK so is subject to more rules but nothing like it would be if it was a formal group. As another aside, Audax United Kingdom Long Distance Cyclists' Association ("AUK") is an affiliated group of Cycling UK.
However WC and AUK are very different in structure. WC is an unincorporated association whereas AUK is a company limited by guarantee.
There is no statutory definition for an unincorporated association, but a number of definitions appear in case law. The most well-known definition comes from Lawton LJ in Conservative and Unionist Central Office v Burrell [1982] WLR 522, who defined the entity as "two or more persons bound together for one or more common purposes, not being business purposes, by mutual undertakings each having mutual duties and obligations, in an organisation which has rules which identify in whom control of it and its funds rests and on what terms and which can be joined or left at will".
It is a structure that most clubs adopt almost by accident when they are formed. Legally it could probably be argued that ACME is already an unincorporated association as none of the rules need to be in writing. The only thing that could be a saving grace is that no one has asked for or paid a subscription. I understand that ACH is free to join and I assume it lives off a small surcharge on the kit it sells. Perhaps someone could reach out to ACH or ACB and ask. Keeping it simple has a real attraction here as you will find out below.
Most clubs do go on to have some basic rules and safeguards to prevent Arthur Fowler Xmas Club situations and to deal with a range of issues including:
The name of the association;
The association’s object and purposes;
Election and admission of members;
Payment of subscriptions;
Resignation of members;
Suspension and expulsion of members;
Composition of the managing committee;
Management of the association’s affairs;
Finance and property;
General meetings;
Alteration of rules;
Dissolution of the association; and
Power of specific officers to bind members.
The problem with unincorporated associations is that they have no legal capacity as an entity separate from their members. This becomes an increasing problem as they become bigger and need to deal with third parties. At this point most will appoint a committee to act on their behalf, which brings its own list of new issues, and many will become companies limited by guarantee. There are other structures that may work for a group depending on what they are doing. There is also a tax efficient structure for Community Amateur Sports Clubs that many local sports clubs will sign up to.
There are liability issues as well. It is not possible to sue an unincorporated association as it has no legal personality. It would theoretically be possible to sue all the members of an association if the association at large was, say, causing a nuisance. Normally, however, it would be an individual that was sued. Most of us carry third party insurance by being members of Cycling UK or the correct grade of membership of British Cycling. Huggy has already identified the real issue with liability in relation to WC, an individual being held liable because of something they do on behalf of the club. This why the velodrome insists on club insurance cover. It is hard to see how this could really be an issue as the only thing that ACME will do will be to organise certain audax events and these would be covered under AUK's policy. It may be food for thought though.
You will not be surprised to hear that the only real exceptions to the legal entity point are tax and anti-discrimination rules (though in both cases there are de minimis rules in place).
If anyone is still awake and at the risk of being even more boring, if we are going to end up as an unincorporated association, it does probably make sense to have the most basic set of rules imaginable in place at least. These rules are usually as much for the protection of those looking after the money and members as they are for the members. Fortunately there is nothing new under the sun really when it comes to this sort of thing and it should not be hard to create a set of rules. I was thinking that the amounts we are talking about are not large and it was a bit of overkill but Tomsk is potentially about to create an order for c. 2k worth of jersey and caps so perhaps the amounts are not trivial after all.
At least on this occasion it really is alright to blame Oaky as he came up with the concept in the first place