My exH and I separated 2 1/2 years ago after 15 years, the latter half of which were unhappy - he was unaffectionate, uncaring, unsupportive, belittling and emotionally and financially manipulative. I was on anti depressants for most of the marriage but - surprise surprise - was able to come off them soon after we finally split as the relief was enormous. We have 4 children together aged from 11-17, the youngest of whom has complex medical needs and is often unwell and also admitted to hospital several times a year. They live with me and see their dad eow with a week at Christmas and in the summer holidays. I have a new partner who has 2 DC who live with their mum and we have just moved into a new house together and are expecting a baby in July. ExH has a girlfriend who has 2 DC. Background more or less over!
ExH isn't very involved with our DC. He likes to be fun, Disney Dad and not get involved with day to day school, medical, behaviour issues etc. This has always been the case and is one of the reasons I was very unhappy with him. He told me that he was responsible for going to work and that he shouldn't be expected to do anything else. For example, DC3 (age 14) has an operation on his leg last week, I let his Dad know that this was happening but he has not been touch to ask how it went or how DC is. 
He does however like to tell me what I should be doing with the boys whilst also telling me that he's too busy to be practically involved. He tells me I'm a poor parent who doesn't try hard enough with the DC. For the record, I am a SAHM mum due to my youngest sons medical issues for which he gets the highest rate of DLA and consequently I receive Carers Allowance for him. I am very involved with school, social lives etc and am always around. DP and I arrange our lives around our children as we feel they are the most important parts of our lives and often cancel our plans during a "free" weekend because either one of the DC is ill of they want to do something other than go to their Dad's. It is telling that the staff at the local hospital where my DC4 has had open access since he was a newborn think that my DP is actually his dad because his actual Dad has been so uninvolved!! I accept all of the short notice changes of plans etc as part and parcel of parenting. ExH expects me to fit around his plans because, and I quote from ExH, he "works hard and deserves to do what I want with my free time without justifying it to you". Fair enough but I am annoyed that this free time doesn't include spending time with his DCs!!
When I question ExH's lack of proper involvement with the DCs I am accused of being mentally unstable and abusive - I consequently save all messages both to and from ExH to prove to other people that this isn't the case! He has never been able to accept that he is anything but perfect and has always told me that I am simply being deliberately nasty when I disagree with him. He expects me to tell him about every detail of the DCs lives and insists that its my responsibility to do this and that he should not be expected to contact me or the boys during the 12 days a fortnight that he doesn't have see the boys. He doesn't ring them or make any other contact with them although he lives 15 minutes away and I have always told him that he can see the boys above and beyond agreed contact times.
The current issue is that ExH has apparently now decided to only communicate with me through the DC's. He was meant to collect them today to go to him for their 2nd Christmas with him (we alternate Christmas) but he refused to answer any messages regarding this and instead told me via DC1 that he wouldn't be collecting them until tomorrow as he had made plans and wouldn't change them. I was meant to travel with my DP tomorrow for the 7 hour trip to collect his DCs before doing the return journey on Sunday but now will be unable to do this. He is also returning them on New Years Day and not having them for a full week as is agreed. This is because he says he couldn't take Friday off work - he gets 25 days holiday a year once 3 days are deducted for his company shut down over Christmas and last year took just 4 days off for his children and took the rest for himself and girlfriend and her children - again, because he "works hard and deserves all of his holiday".
Does anyone have any suggestion for how I deal with the current situation? I am unhappy about his refusal to discuss any plans with me whilst expecting me to tell him everything. It's not appropriate for him to use his DCs as go between a.Currently I would sincerely like to lamp him when he collects the DCs tomorrow but expect that will just have to remain an internal fantasy!!
I know compared to other people's problems that this isn't a particularly big one but I am frustrated and fed up of this. I think he's just doing this because he can tbh. It's a control thing.