Firestormm, when you say "there's probably more", well I think there probably aren't.
Suzy has listed the 6 that I'm aware of. There are of course other organisations and local groups which aren't charities, which may confuse the picture, but I think there are only these 6 UK charities. Unless anyone can name another that's missing from that list, which would be interesting.
As I understand it...
The ME Association is the oldest ME charity and, in that sense, the original.
ME Action, as I understand it, is not a registered charity but it split off from the MEA when they changed name from "encephalomyelitis" to "encephalopathy" - that's the disagreement over nomenclature.
TYMES Trust: for children and young people specifically is a legitimate reason to have a separate charity IMO.
Invest in ME and ME Research UK are both primarily concerned with research and again I think that's a legitimate reason for a separate charity with a different and dedicated focus. Invest in ME in particular has quite limited and specific objectives and it's a success story from that point of view because it is extremely effective at fulfilling that objective with minimal costs and overheads. These two have slightly different focus in terms of the work they do, but it does seem conceivable they might be usefully combined into one organisation.
I do agree that there might well be some value and mileage in combining these 4 charities into one, stronger organisation. There might be some organisational
inefficiency in doing so too, but I think there are plenty of people who wonder why there aren't fewer, stronger voices. I don't know enough about it but I do wonder whether it would be feasible for Invest in ME, ME Research UK, the MEA and
perhaps also the TYMES Trust to work more closely together, combine, or federate in some sense - perhaps something like a Coalition or some other kind of forum where the various organisations can discuss working together, perhaps even feasibly one could imagine they could be combined into one charity with research and young people's 'divisions'. I don't really see major ideological or political differences between these 4, although perhaps there may be some personality clashes. If there
is a clash, then my guess would be that the other 3 organisations aren't entirely happy with the focus and leadership of the MEA. Personally, I would rather like to see those 4 organisations combine into a bigger and stronger organisation - I do think there might be some benefit in that.
But with the above, there are 4 charities, one for young people specifically, two for research, and that wouldn't really be complete overkill on its own in terms of having too many charities.
Where the situation then becomes complicated, in my opinion, is when Action for ME and AYME come in. I don't know about the history of when, why, or by whom Action for ME was formed, and who decided that a separate national charity to the MEA was required. That history would be highly relevant to the question Firestormm raised, because really, in terms of major national charities with a generic focus, there are only the two: Action for ME (and its 'youth wing', AYME), and the MEA.
My perception is that it would be extremely difficult and almost impossible to reconcile AfME and AYME with the other organisations: their image is tainted in the rest of the community by their perceived associations with the psychiatric lobby and government interests. It would take an awfully big change for the rest of the ME advocacy community to trust those organisations enough to work with them, from what I can see. AfME can't be ignored, though: they have a very large budget, I haven't compared it with the MEA's but they are substantial in size.
The way I would see it: If one wanted to see a closer union between the various ME charities, the most realistic might be to imagine the first four charities amalgamating in some way - or being in some sense 'absorbed' as divisions of the MEA, which would require the MEA to change in the process - with the aim of creating a larger organisation capable of challenging the perspective of AfME. I agree that the scene can appear confusing but when you break it down, there really isn't such a large number of charities after all. By comparison, there are several cancer charities, with different focuses on research, child support, adult care...
Anyway, that's my rough overview of the scene, and I'm sure there is much that some people will want to challenge in what I've written above, and much that I haven't fully understood, so I look forward to reading some more views on this...