Absolutely. You can use your sync. card in countries whose currency is not yet available with sync. The funds will be debited from your default currency account, for the UK it would be your GBP account and for Europe, it's your EUR account.
If you are prompted to choose the currency you want to be charged in when using your card in another country, we highly recommend choosing to pay in local currency.
Selecting to pay in local currency means your home bank handles the currency conversion. Should you choose to convert to your home currency at the time of purchase, not only will you pay additional fees for the privilege, you may also receive a poorer exchange rate.
This applies to both ATM and merchant terminals.