All of the cell phone companies seem to be saying right now that it won't make a difference, but I agree, there's no guarantee that there won't be significant limitations after Brexit is fully effective. Market conditions rather than EU regulations will dictate the result. Even with changes, my primary use in the UK/Ireland probably won't change because of the close connections between the two. And since Ireland is EU (and Northern Ireland now seems to be some sort of hybrid), I'm hoping that the status quo will prevail for my uses in the rest of the EU.