google assumes everyone is in the US,

Scroll down to below the search results, there will be a location mentioned that's used for the searches, with options to change that to your liking.

thanks but that doesn't actually stop lots of wrong location answers...

Please appreciate you'd need to ask Google to support their search service.

There's no difference in forcing country level domains as Google moved off most of them in the recent months and years and they use other signals to decide on the geography. If setting a search region and checking your locale (i.e. iPhone settings "region") is not making any difference, then besides setting more search prefs in google.com/preferences I can only advice changing your search provider to a service that yields more relevant results. I assume Google uses your IP address to adjust the results, but expecting your residential or mobile IP would geolocate you correctly, so that's all the browser or device can do about it. You can verify on www.whatsmybrowser.org that your language shows as en-GB there, and iplocation.io gets the right data for your connection.

Thanks for your reply

Maybe a tip that could help, albeit it's slightly convoluted: Firefox iOS allows setting any URL as the (default) search engine, so if you have a specific set of Google search params that you'd like to use as your default search, you can add that alternate URL as a e.g. "Google (custom)" and use this as your search provider going forwards. I personally use one with slightly modified &udm= values. Not sure if that can change anything in this case, but if your results look better with explicit &gl=uk added, you can turn that into a search provider entry of your own.