Long story short I have a (nearly) 8 year old Ds with my ex. The relationship was not good by any means but I was young (15) when we got together and didn't know any better. Throughout our relationship he showed me numerous times that he was an arsehole but I ignored it as we had Ds and I thought he would eventually grow up and change/take responsibility. He didn't and at the end of our relationship he hit me and that was that as far as I was concerned. Ex and I never lived together for the 5 years of our relationship, which was his choice.
I then made the decision to take Ds and move to the UK to be around family as I was living in Ireland at the time, I told ex of this plan which he just sort of shrugged at 
after speaking to his parents however (and after our plane tickets were booked) I received a court summons. The up shot of this was that I was denied the right to move. I appealed this decision and the case was looked at again by a different judge who decided it was in mine and my sons best interests to be allowed to move. I would however have to facilitate visits back to Ireland so my son could have contact with ex. Dates etc were all discussed.
He also never paid a penny towards Ds until he was 4 years old (after the split and during our first court visit he was ordered to pay weekly)
It has now been 4 years since all of this and in that time ex has become less and less interested. Goes weeks as sometimes months without paying maintenance and always has an excuse (like needing money for his brothers wedding ). In our agreement it says he is to visit 3 times a year. In the last 12 months he has visited once and in the 12 months before that twice so it's dwindling. He has only ever been the full 3 times once. I have to bring me son to visit 5 times a year which all fall in the school holidays obviously and cost a fortune, as well as having time off of work etc.
This was so much longer then I intended I'm sorry 
Wibu to speak to ex about this? He is obviously struggling to pay the maintenance/has better things to spend it on and I am struggling to fund all of these flights especially when he stops paying as and when he feels like it anyways. If he were to pay the maintenance religiously ever week it wouldn't even cover the flights let alone raising Ds anyways. I'd like to reduce the 5 visits to 3 in exchange for cutting the maintenance in half? Does this seem fair?
I'd just like to add that Ds does not benefit from a relationship with him or his family. He does not want to go (an opinion he has formed himself as he has grown, honestly has nothing to do with me). Ds would have no problem with reducing visits whatsoever.