I am a payee and I am repartnered. ExDP is also repartnered with a new child and a partner who doesn't work, we have a private arrangement and it works for us because we are amicable and understand that life happens. He will pay more if I ask, and I understand if he can't pay here or there. At the moment he is back paying 3 months of CS at a small amount each week as I understood that things happen and come up.
I think that there needs to be more support for separating parents to understand each other and not do the he said/she said, he gets/she gets attitude that gets thrown around so regularly! There's so much bitterness in separations so peoples feelings get in the way of what's important - ensuring the kids are well look after.