So, if somebody says you cannot do XYZ, they need to provide a reference for that.
Absolutely. Unfortunately the lady from the CAA just kept on repeating that this was nothing to do with the UK and any reference would have to come from the specific countries I wanted to fly in.
All I wanted was confirmation that the default position (at least in Europe) is that I'm allowed. All she would say was that nobody could state that as it was up to the individual country.