When is a contract not a contract? In Family Court

I am a 49 yr old British pilot working in the Middle East. My ex-wife, who is a Kiwi but holds a UK passport, and I separated in 2009. She left me and our children. When she left we agreed terms: she gets all our savings, she keeps her business ( totaling about $100,000 NZ)and I pay for all our children''s needs, education, home life etc. We had no property and I still don''t own any property. She wrote to me after I transferred all our funds to her account thanking me and telling me she would never ask anything of me again. Since then I have honored every part of our agreement and more.
Our lives went in different Directions and the children lived with me. I have paid for all their needs, education etc and am now paying for our eldest sons university course. Now after a series of poor decisions on her part she has found her life has not (as I warned her) turned out as she planned and she now (according to her) finds herself in a poorly paid teaching job (in New Zealand) and close to £40,000 in debt. She filed for divorce in the UK because she knew she had no case in NZ, but knowing the UK courts will look favorably upon her case. She now wants half my savings, half my pension, payment for all her legal fees and wants me to pay for all our youngest sons (16) living costs (he moved to live with her in NZ 12 months ago). According to the lawyer representing me she has a good chance of getting everything she is asking for because she is now comparatively poor and our son lives with her (the mid East is not a great place to raise kids).
I believe I did everything in accordance with our ''contract'' and I am not responsible for her subsequent poor lifestyle choices and decisions. However, it appears the UK legal system takes a different view.
I would like to argue that we had a contract which I honored and I should not be held to ransom for another persons independent choices.
Can I take my case to the European Court?

The leading authority on nuptial agreements is Radmacher v Granatino. www.familylawweek.co.uk/site.aspx?i=ed68495

Although they cannot be enforced as contracts, agreements, if there are no vitiating factors can be given significant, sometimes decisive weight when considered by the court. However no agreement can compromise the needs of a dependent child.

There is no need to go to the European court, the UK court will, as part of the financial order process, consider the agreement.

When there is full financial disclosure, both parties took legal advice & an agreement is fair (complies with s25 Matrimonial Causes Act 1973 & other law) the agreement carries considerable weight & the court may make an order in the same terms as the agreement. Otherwise informal agreements not drafted by a solicitor aren''t recognised & your solicitor is correct, your former wife will be able to claim against you. All national remedies need to exhausted first before before applying to the European court/ECHR.