Thank you for your reply Niceguy2 and I'm sure you realise that every situation is different. Things might be different had I walked out on the family, but I didn't, I stayed and took all the cr*p. What is different now is that I am now asserting my position, and stbx doesn't like it.
I am accutely aware that my son is entering into teenage life and I have fully considered this with regards to my proposition. However, stbx is now living with a new family of 2 boys, of which our son is in the middle. This has caused some anxiety for my son and, of course, me. Although, he is doing really well coming to terms with it...in fact, I'm really proud of him. I know that I can continue to support all the children and do this with every encouragement that they develop a positive relationship with their Dad. As regard expenses, I have said that I will contribute to his costs for seeing the children, including travelling with the children to see him.
What is 'unfair' in all of this is the fact that my stbx was personally unhappy for some time and chose to leave the family, knowing full well it was an extremely difficult time, without addressing any issues he had with me. It transpired he had been conducting an affair for some time - yes, with someone slimmer and more attractive than me. Hindsight is a wonderful thing. Previously he conducted an affair during/after our 3rd child was born and at a time when a close family member of mine died - he chose to tell me on Valentines Day. He refused to talk about it then and afterwards, but I took him back believing it was for the greater good. I now think I was wrong. I put up with years of living with an extremely unhappy person, who refused to talk about issues with me. I just got on with it and he still sh*t on me.
To answer your q ...the kids see their Dad every other weekend and half the holidays... in fact over the next half term he only needed to take 2 days off, but instead they are going to their grandparents in NW England. This is a recurrent theme in 'his' contact with the kids.
Don't get me wrong, I'm fuming, but I also know that I have to bring the children up for the next 10 years and will do to the very best of my ability. Maybe he was right, he left me because 'we are different people'...says it all.