Originally Posted by
Some person
I think that terminals only can identify the country of issue but not the currency of the card. This probably means that all UK cards are identified as GBP cards by the terminals, despite a small percentage of them being denominated in other currencies.
IIRC the currency is on the chip too. It could be that the Euro denominated British cards are set up so that GBP is given to the terminal despite how they behave otherwise.