I think we are mixing up two different things here: a local London meetup and a UK SIG.
The local London meetup is to exploit the possibilities of face-to-face meetings. The more people we can include the better, and maybe thinking about multiple locations might be worth a thought as well if it increases participants, but if someone is not close enough to London area to attend, then it makes no difference if that person is Birmingham UK or in Amsterdam NL: we all would love to make a Fedora meetup that allows everyone around the world to participate, but this is not realistic. So we have to do a London meetup, not UK. If it gets digital to avoid geographical limitations, then there is no reason to limit it to UK but then it would be a global event anyway, and in such a case, we are back to the Fedora meetings that already exist.
However, what you describe is a Fedora UK SIG. I do not know if geographic SIGs already exist, but they inevitably would overlap with functional SIGs, and overlaps inevitably lead to interaction and outreach. So that is indeed worth a discussion, and it would be complementary to the Local London meetup (and as such worth a point on the agenda). But it is still two different things, and we should dedicate a topic for that if there is an intention to create a SIG like that. It should contain a clear emphasis in its activities / goals from the beginning, but given what you say, your initial goal might be to “incorporate” the activities that used to be related to the Ambassador, or identify an ambassador and support them in their activities. As far as it concerns me, I would be happy to help with admin/org stuff if you need help with that, but I am not sure if I can contribute much more to that.
But in any case, I think we should not merge a local London meetup and a potential UK SIG. So I suggest to open a new topic for that? And maybe link it to the UK channel so that others can consider it as well?