Cuckolding - complicated emotions, complicated subject. Scares the hell out of a lot of people - including the majority of swingers - so in many cases it's advertised on sites as NSA sex and the other party may never even know (as you did not) that they are in this arrangement.
Part of the "thrill", either for the wife or hubby or both, is usually the wife teasing hubby ( where the guy was looking at you in the pub?)
The other guy MAY be Bi, but then again he may not. For an entertaining insight into this scene have a look at Stanley Kubrick's film Eyes Wide Shut.
I can understand your point of view that you were not informed about it - essentially someone else was being a voyeur into your sex life without your consent. However, at least they came clean with you and gave you a choice. Chalk it up as an experience in life and move on if it is getting too heavy - which it sounds like it is!!:boxing:
In response to the op I read both your posts, I think to a lot of people they don't get your concerns. Yes it is about two adults consenting to have sex, but you never had sex as two people as there was a third party involved.
She was honest about being married, maybe you should have thought longer and harder about the consequences about what you were getting into at that stage. Hindsight however is a wonder thing.
Like other here say it is about NSA fun, but I have always believed in honesty so people can make an informed choice.
You now find yourself in what could be a delicate position whereby they have videos of you which could now be used against you if they wish. Luckily it seems you have a copy also, judging by your posts.
I am a female from a couple, in the past when I was meeting hubby would at some stage talk to the guys beforehand with me, all on cam together face to face to reassure them we were in this together. I have always felt it is about putting the guy at ease as much as them putting us at ease to invite them to share in what we do.
I feel the couple you saw(as it was a couple) even if they were a cuck couple, were not totally honest. Some would say it is your fault I believe it is 6 of one and half a dozen of the other. If she had said she was single and then you found out she was married I could understand you more, but maybe the lesson to learn from this, is next time you think you are screwing a mans wife behind his back, just wonder if they are in fact screwing you to.
If they had an open relationship and lead their lives that way, then maybe you should have just asked to have seen them both on cam and had a brief 5 minutes together. So you can establish if he fact there is consent on both parts. If they didn't want to do that basic requirement maybe you should have walked away.