My dd is now 11 so it's not something I am currently dealing with. There is SHTF prepping which I do and there is Brexit prepping which people lurking on this topic might be doing. People might move on to SHTF prepping or they won't. Personal choice.
So as not to discourage Brexit related lurkers, I'm going to add what I would do now:
Start using reusables and get baby (and you ) used to driving them. If you can make them yourself or can get a friend to, so much the better because you can customise them. We may have absolutely no problems whatsoever with supply of your favourite nappies to the supermarket post Brexit. Or we might. Even a little bit. Loads of info online.
I struggled to bf due to health problems so that wasn't an option for me. For anyone in the same position, I can think of no alternative to buying tins of powder and making sure your formula preparation is good enough to cope without any gadgets you might currently use.
Any others?