"If you have children or property, I would strongly recommend getting proper legal advice."
Absolutely. Maintenance, pensions and Succession rights are often forgotten by lay people and do need to be addressed.
"From a legal perspective it isn't worth the paper its written on without being backed up by court orders."
Not really. It can be a problem when the parties are not legally represented and subsequently use that as an excuse/reason to re-visit contractual terms BUT when both parties are legally represented and agree terms which are intended to be binding, a Court will be slow to upset any such agreement.
"all property for a married couple is considered to be jointly owned in the first instance."
This is a common misconception. It is more correct to say that , in the event of separation and/or divorce, all assets whatsoever can be taken onto account, by a Court, when making Orders with the concept of "Proper Provision" in mind. Different relationships can be looked at very differently by a Court.
Twenty somethings, no kids and property gifted by Daddy to one, is very different to the seventy somethings, a lifetime together and lots or few assets in joint or sole names.
mf