Dan, I think your response to her above sounds good. I would also suggest you pursue the option to make it legally binding just to protect yourself in the future.
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We have no kids and have already agreed what we'll do with the house proceeds (50/50) and agreed who gets what in the house (all itemised lists). We have also stipulated that personal accounts and credit card debts in individual names will not be shared. We just have one joint account which will be split 50/50 after all costs have been paid. Am I being too naive here? In the UK we don't seem as litigious as the US.
Not at all, I think we all have a certain amount of paranoia when going through D that we're getting secretly screwed somehow but it sounds like you are both in agreement on all the terms so I don't see an issue. My XW and I agreed on everything, she drafted it up, then in the 11th hour demanded more money in an email that made absolutely no sense at all. I asked her to explain but she just threatened to fight it out in court so I told her "I don't understand why you are requesting this but I trust that you feel it's a fair settlement so I will sign it." The bottom line, no one is "made whole" in divorce. Both parties have to give some thing up. It's a good idea to get advice from a lawyer, but I'm all for avoiding a court battle (unless it's absolutely necessary) because it just fosters bad blood and costs both parties a ton of money.