My wife and I traveled for 24 days in April 2014 to Ireland, Scotland, London and Paris. We brought a few hundred US dollars but did not exchange any, per RS suggestion. The US dollars were for emergency situations only, i.e. bank strike, bank holiday, etc. We used ATMs in every city with our debit cards. The exchange rate for the local currency is about the best you can get and fees are usually none or very small. At the end of our trip we had some pounds to exchange back to dollars and the rate at a currency exchange company was terrible with an added commission fee. Glad we did not do that too often. Before we left home we contacted all of our credit and debit card companies and let them know the location and dates of our travel. There were no problems with rejected charges during the trip. We paid for most everything with cash on the trip. It was just easier. Large expenses like hotel rooms were paid with a credit card, VISA or Am Ex. All plane, train and tour reservations were made before we left home with credit cards. We set up an alert system with our debit card company so that they sent us our balance every morning on my smart phone. We, therefore, were able to confirm any charges or ATM transactions. It worked great. Having a smart phone was a major advantage. Many apps are available which help with buses, trains, planes, all public transportation and local maps. No need to stand on a street corner with a big old paper map looking like a couple of lost tourists. Also not too safe. Set up a data and voice plan with my phone service carrier. Really didn't use the voice but racked up about $75. worth of data charges when we could not use WiFi. It was well worth it. Used the phone everyday to plan our day and get directions. In Ireland we did a nine day tour so stayed in different hotels. It worked out OK. All pre-paid. On our own in the other cities, we rented flats through VRBO, HomeAway, Trip Advisor, etc. Much cheaper than hotels if you are staying for more than three days in a city. Also had a lot more space and did not need to eat out every meal. Restaurant food is a significant expense particularly in major cities like London and Paris. Hitting a local market and getting breakfast things and other food saved a lot. But, of course, need a refrigerator to do this. Therefore, the need for an apartment. When we used an ATM we hit it for the max 300 pounds or 300 euros to minimize the number of transactions and therefore, the number of extra fees. Worked out OK. We probably averaged 30 to 40 pounds or euros per day for everything just because we did not eat out a lot. Everything included transportation, whatever food, souvenirs, small other expenses. Get an Oyster card in London for public transportation. Carnet (groups of 10 tickets) in Paris worked well. We were in each city for five days. A money belt is an absolute necessity. Don't be paranoid but pick pockets are a very real issue and problem, particularly on public transportation and where there are large tourist crowds. Just secure your valuables and always be aware of your surroundings. Losing your money or passports can put a real damper on what could be a wonderful trip. Just plan well, do your homework and enjoy.