Problem in the UK is financial settlements can only be 'forced' as part of D.
This can't be, can it? Shouldn't any two parties be able to create a contract to sell a joint asset and then separate the proceeds in such a way as to make those proceeds immune from any future separation agreement? Sounds like a post-nup agreement.
This was rhetorical, the answer is that of course two parties should be able to agree to whatever they want. Unfortunately, the enforcement of post-nuptual agreements varies from jurisdiction to jurisdiction.
I'd rather have some sort of agreement in place, signed off by both party's solicitors, and make him have to invalidate that in the case of an eventual D settlement, than to have nothing at all.