People can do BFA whenever they want, you can also do one when doing things by consent through the courts to cover some things.
Only you can decide what best suits you, if you have agreement with your former other half, I would get that in writing ASAP, you can at the same time get legal advice on your specific situation. All I know is when it is concluded through the courts, it is hard to undo unless certain things have happened such as fraud.
So all I would say is, get advice independent from your BFA, you will need 2 different lawyers to do it. I guess what I am saying, is try and make the BFA as binding as you can.
All the best.