US exchange for Euros at ATMs at LHR

The ATMs in Britain will dispense British pounds. If you find a machine that offers other currencies, it will no doubt belong to an exchange bureau and you will pay conversion fees by way of a poor exchange rate. Why not draw Euros from an ATM in Athens? I understand you're arriving late, but surely an ATM there remains open in odd hours. I'm sure you could find an ATM at the airport in Greece, too, and not have to worry about withdrawing cash on a dark street corner. That said, personally I like to travel with some local currency already on hand upon arrival. Local exchange bureaus in the U.S., or AAA, or American Express offer travel packets of Euros. I like to take about $125-$225 USD worth of local currency in small bills for snacks or taxis when I arrive. (And yes, I do convert an odd amount of dollars frequently because exchange bureaus (and ATMs) like to distribute larger bills and I try to tailor my order to force them to give me at least a few Euro in coins or small bills.) If you have a credit card with good exchange policies ---I use Capital One --- use it at Heathrow to get yourself a meal or a souvenir. Six hours seems hardly worthwhile withdrawing any pounds and trying to convert them to Euros or dollars later.

As Matt said, you will be buying those €uros. In fact you will be paying twice if you do it that way. You will be buying €uros from an expensive currency exchange machine and you will be paying the machine in Pounds which will then be converted again to the Dollars in your account. Far better either to buy Euros before you set off, or even better to use an ATM in Greece (if it is still there when you arrive) for the cheapest go at it.

ATM's don't close and they don't take bathroom breaks. You should be able to withdraw euros when you get to Athens. Ask someone in a uniform or at the foreign exchange counter where the ATM is. There's often one in the baggage retrieval area, so you could get cash, pop into the toilet and stuff most of it in your money belt, all before your luggage tumbles down the carousel. It has also been my experience that the foreign exchange counters are open whenever there are flights in or out. Just have some US cash to exchange in case the ATMs are all kaput. You're likely to get a better exchange rate at the airport than in the US anyway.

Another thought. Since you have the time at LHR, ask if there is an ATM that dispenses euros. Here in Israel, there are several ATMs, including a couple at the airport, that dispense US$ and euros, and the exchange rate is usually very close to mid-market.

We have used the ATM machine at the Athens airport many times without a problem. It is located on the other side, opposite to where you exit from customs and baggage, I believe near the information desk. When you exit through the double doors, look across the corridor, for a waiting area with a few rows of seats. The ATM is off in that corner beyond the seats. There may be other machines in the airport too, but that's the one I am familiar with.