My ex and I were married in the UK but divorced abroad. I am now back here with our children and he has also moved away from the country where our divorce was finalised.
We have joint legal custody and I hold sole residential custoday. He has signed a letter stating he allowed me to move back here with the children and I agreed to allow the children to visit him (long distance) in his place of residence for most of the holidays.

He also insisted he could slash the child maintenance almost in half since the cost of living here is nto as high as our previous place of residence. Me agreeing to this was really his only stipulation for allowing me to move away with the children.

He has now also relocated to another country and insists I am solely responsible for the cost of our children flying to him as unaccompanied minors. In the past 8 months I have paid out around 2,100 on flights for the children and am now falling behind on my own household bills!!

He does not contribute to extra curricular activities nor to school trips etc.
Is he right in thinking that I am solely responsible for these costs or is there something I can do here??