None of us will ever know what was going on, so this is a completely pointless argument (in keeping with how I like to spend my time on redcafe!) but it just feels like the sort of uber-dark, dysfunctional vibe the show usually goes for that they’re both constantly fecking around and both in complete denial about this. Which results in what looks like a happier/healthier relationship than the two normies who are trying to keep a much more conventional relationship above water.
I get what you mean but I wouldn't say they were happy. There was one look in particular in one of the later episodes when the guy out of the inbetweeners film was brushing his teeth, his wife shouted him a few times to come speak to the kids on the phone and he looked miserable, had to steel himself then emerge all happy.
They were acting even more for me, at the least the other couple recognised their issues and were trying to work through them. Which ultimately led to the banging again and finding happiness at the end..
That's the way I saw it anyway, but I think your right, the show for a while made out everything was rosy between the cheaters.
Edit, sorry I completely miss-read your post haha, I guess I am saying the same thing