If I was you, I'd write to Facebook and ask them for advice on what to do. It's a totally valid question to ask.
You may get all sorts of incorrect answers here.
I live in Australia and we use GST, not VAT, so I can't help. I could only make a guess based on my GST experience. But I won't as it may be totally wrong.
BTW, I'm not sure if you are trying to setup a "business account" or not. If so, you don't need a business account to run ads. You can run them just as an individual. Business accounts are only really useful for people who have multiple stores and/or multiple account managers. For a single store and manager, it's overkill.
Here is the info on whether you need a business account. It's for Instagram, but that's owned by Facebook so the rules are the same ...
https://www.facebook.com/business/help/1010682245633077
I just use my personal Facebook account to run ads and have never been asked to provide a VAT or GST number.
But to be 100% clear, I would still write to Facebook and ask for advice.