When I say stand up argument, they were actually sitting down at the time - but it was an argument and DH texted everyone to apologise the next day and we have seen them all to talk to since then.
I'm sorry and this is going to be annoying. We've decided to go, it's easier than not going, and we will be on our absolute best behaviour and just smile and nod and not drink.
The other couple have suggested a date already, so the invitation is very much on. If we say we aren't going it will damage my friendship with the two women which I want to keep up.
Thanks for all your opinions, they are very welcome. Having slept on it I think it doesn't seem such a big deal this morning.
Hosts are couple A - they are grumpy and bicker with each other all the time so it's never any fun being in their company. Other couple, couple B - she can turn on her husband at the drop of the hat and it can get uncomfortable. DH and the wife of couple B rub each other up the wrong way it's actually because they are very similar, they don't know when to keep quiet to keep the peace.
I find the husband in couple A rather hard work but do like the husband of couple B.
C'est la vie, I guess. I'm not keen to have a regular going-out-as-a-6 thing like our hosts seem to be but as long as it's only once a year I think we can do it.
Hope I haven't wasted anyone's time 
.