I was reading:
Domicile of origin
Everyone acquires a domicile of origin at birth. This is usually the country that your father considered to be his real or permanent home at the date of your birth.
Your domicile of origin will continue until you acquire a new domicile - therefore if you have a domicile of origin outside the UK, then this is likely to still apply unless you intend to remain in the UK permanently or indefinitely.
I'd say that my permanent home is outside the UK (even though I have just got family/friends there, not a physical house for example) but HMRC could say that the UK is my permanent home as I am a British naturalized person now and with a physical house here.
Following the same definition, my children could say that they are non-domiciled as they want to go outside the UK in the future but HMRC could argue that they are a British born person who has always been living in the UK and as such the non-domiciled status does not apply to them.
My main doubt is that I think I am not domiciled (and neither my children would be, even if they're British and I become British) but HMRC could say that that's not the case from their point of view.