Relate are pretty much the only group doing marital counselling.
But the thing is, if they don't want to go to counselling, if they don't want to change things, there's nothing you can do, really.
Ok, that's not quite true, I got fed up with my parents rowing all the bloody time and whinging about each other, and confronted them about it, and offered to pay for counselling, and explained how miserable it was making everyone else.
It was fun.