This thread is like The Twilight Zone!
Nary a week goes by, there are a couple up right now, without a wedding thread featuring an invitation where one party's spouse or partner with kids are not invited, it's childfree, destination wedding, and the overwhelming response is 'Can he not go on his own' or a thousand different variants on how he should go and she should rope in someone to help with the breastfed newborn and toddlers after a planned CS or sit in a hotel room or cottage whilst he skips along to the wedding or plan a family holiday round it all with the rest of the family not going to the wedding. Every week.
Or a bride stating she and her fiance simply cannot afford +1s or kids and it's all 'Your wedding, hun, you do what you need to'. 'It's fine, if you can't afford it or that, it's your wedding.' Not everyone can afford +1s. Plenty of posts on here about venue limitations so no +1s.
But this guy is supposed to drop his 'good friends' entirely because they didn't invite his girlfriend of 10 months to their wedding where they live, in S. Africa? Or bamboozle them about why she wasn't invited? It's 10 days! And nary a long time goes by without someone who waves their spouse and/or father of their children off to one of these shindigs.
It was majorly crass to hand out invitations like that. I do have a good friend who lives in a part of SA (near the Zim border) who cannot trust the post there, but it was rude to hand them out knowing you were not invited.
But honestly? I wouldn't have expected to be invited and I think your big problem is considering him 'DP' when he doesn't seem to be at that stage yet and nor do they and you were fine with him going to the stag until you found out you were not invited.
Hell, we eloped due to some serious issues and people managed to get over it.
But seriously? He's not only not supposed to go but also tell them all to get to fuck for not inviting his girlfriend of 10 months?
I think it's really petty to stop associating with them over this or be PA or expect him to confront them over whom they invite to their own wedding.
FFS, being a 'singleton' at a wedding is hardly a disaster scenario, especially if you're with good friends.
Totally OTT, IMO.