ah how I love waking up to a conversation with 'cuntybaws' and 'piss in your mouth' on a sunday morning... :)
Regarding the meetup thing - I think it's different from being at a christening or work do or something when it comes to social dynamics. By definition, everyone there is meant to want to meet people, male or female, and if some woman has a problem with her OH chatting to attractive women, that is her/their problem. If she doesn't want him meeting up with new people, they shouldn't be going to a thing specifically designed for meeting new people. I'd say you can chat to whoever you want, just keep an eye out for the wedding ring if they're getting too flirty.
I like OD for it's straightforwardness - you're meeting people who want to date, want a relationship or something casual, but they've advertised the goods, so to speak. Real life is different but more colourful. I have more of a RL social life in Hungaria than I have in several years of being married or single in England, and there are little pitfalls like meeting the Translator, going to the zoo with her and then she says actually she's kind of seeing someone else (who's shagging around and she's annoyed with it but says 'yeah, but what can I do?' in a pathetic kind of way.. sad really)
But RL gets me meeting more people, men and women, and their friends, and friends of those friends, which to some extent replaces the friends I lost when I split from my STBXW. And I'm a social animal, I like meeting new people and talking rubbish over beers, I'm not the scared type who sits in the corner, more of a plonk-myself-down-at-someones-table and discuss their views on the zombie apocalypse (or something) Which is fun.
If I had more time in the UK I'd join a meetup thing. I always thought it was just hill-walking. I bloody hate hill walking.