/As a member of the EU, they could have opted to use the Euro, but they decided not to./
So 'when they were a member of the EU, they could have taken in the euro, but didn't, so still have the pound'
/As a member of the EU, they could have opted to use the Euro, but they decided not to./
So 'when they were a member of the EU, they could have taken in the euro, but didn't, so still have the pound'