Child maintenance calculation when living abroad?

Hi,
I moved to France for work recently after splitting up some 8 months ago with my wife. From the day I left the house I paid child maintenance as per calculations on the CSA website. This was agreed with my wife and there was no interference from CSA etc. We have not yet divorced, she has only just decided to start the divorce proceedings and send me a divorce petition. However, now that I have moved to France I obviously want to continue to pay child maintenance but my financial circumstances have changed. I am no longer living or paid in the UK. My salary in France is lower, I pay a lot more tax and am being paid in euro and not GBP so my question is : How can I calculate how much I should be paying now or who could provide me with this information? The CSA has no jurisdiction in any other country but the UK and I am not employed by a UK company so I understand they can''t help with providing a calculation (which is what I already learned from other cases here on the forum). I have offered my wife what I believe is a fair amount which is what I am paying now. However, she demands a crazy amount and is not being reasonable. Any suggestions on how I should be handling this? She is now threatening to take further legal action. I don''t want to be dragged to court over this, I just want someone to provide me with a calculation that is fair based on my circumstances but she is not being reasonable and willing to talk. I am not shying away from my responsibilities for the children, on the contrary! Any advice would be appreciated.