Hilton live chat is run on artificial intelligence or people who probably have never been to the UK (or ever stayed in a hotel).
A lot of things about Hilton are incompetent.
If you expect the customer service reps of a large multinational hotel chain to have visited every country that hotel has properties in (or think it's relevant), Im not sure the issue is Hilton's incompetence. Individual properties know the specifics of how their rates work.