He talked a lot of talk about fighting me/taking me to court but that didn't actually happen.
Actually he cancelled contact 2/3 of the time or more, often last minute, and very quickly got together with new girlfriends and got embroiled in all their drama, often using it as an excuse for why he couldn't see DS. Had a baby with one of them then split up with her, mother couldn't look after the child so social services asked if he wanted custody and he said no. The child was taken into care/adopted, no contact 
He then went on to have another child with someone else
I think they are still together but I try to avoid finding out TBH. The only reason I know this is because I'm still FB friends with some of his family members so they can keep up with DS.
So DS has 2 half siblings which he has no relationship with.
XP has not seen him since he was 2 and never sent so much as a Christmas card let alone child maintenance.
Contact was stressful while it was happening because of all this stuff I was hearing on the grapevine - GF being alcoholic/into drugs (he had alcohol problems himself) and weird friends that seemed completely inappropriate, DS would come back stinking of smoke and chip fat, with loads of junk food/drink wrappers in his bag (which wound me up because he was only 13 months old!) And I was concerned they were being shouty/smacking etc and DS couldn't tell me. He would often be unsettled when he came home and several times he vomited after contact even though he wasn't ill.
But it didn't last very long. Less than a year. I never pushed/chased for maintenance because I didn't want him to start up contact again TBH, it was unsettling for DS when he would cancel last minute and I didn't think he'd owe us very much money so I didn't want him to feel he had any right to tell us what to spend it on. In hindsight (11 years later!) I kind of wish I had gone after maintenance because it would have added up to a lot! But we've managed fine, and probably it was worth it for him not to feel he had power over me.
I asked a few years ago whether he'd consent to DS changing his surname. He refused. DS needed to travel on an emergency passport 3 years ago so I had to contact XP again to get his written permission for the consulate. He agreed to that one.