Thanks for the heads up concerning pixel and wifi as that was probably my first alternative. I saw an interesting post on Reddit (which, naturally, I can't find now) that discussed the differences between the 2 chipsets that Samsung use in their phones worldwide suggesting some differences in how they roam. Personally, I think it's something to do with how Samsung/Android deal with roaming. My wife's iPhone seems much happier to jump from one provider to another, while my Galaxy S23 will refuse to swap even when I try to force it. We are both with the same network provider (Vodafone UK).
