Today the merchants you can pick for Curve Cash is specifically centered around the UK, and the number of merchants you can pick that are available in other EEA/EU counties are quite limited.
My idea would therefore be to define the list of eligible Curve Cash merchants available for selection country specific, so that the available list would be dependent on the country of residence of the card holder.
With this the cardholder could select merchants that are actually available in their country.
An example of this would be Norway, where non of the groceries stores on the current list operate, for cardholder residing in Norway the list would instead consist of groceries merchants that operate in Norway.
This will make the subscription cards Black and Metal more appealing to non-UK residents.