Originally Posted by ahmetdouas

No that is dangerous. If you go to a retailer in the UK with a EUR denominated card and the seller looks at the card machine and says would you like to pay in GBP or EUR you must always say I will pay in GBP as the EUR rate they give you is on average 5% off market rates, while your VISA/AMEX/Mastercard provide generally spot rate with the bank adding their 2% fee, still saving you money vs. the 5% fee.