Currency exchange is available at many different sources in London, from airports and banks to travel agencies and street kiosks. Always check before changing money, as Bureau de Change outlets need to make a profit and may not offer the best exchange rate. The worst rates are normally from the currency exchange kiosks in central London and the railway bureaux often have high commission rates. Banks and travel agencies usually offer the best rates.
ATMs (Cash Machines)
We live in an international world (and London is a serious international city!) so it shouldn't be a problem finding a UK ATM (known locally as "cash machines" or "cash points") that is compatible with your bank account at home. You can check with your bank before traveling to find out the logos to look for in the UK ATMs. As with anywhere in the world, do be security-conscious when using the machine: check that no one is watching you enter your PIN, and put your money away safely before moving away from the machine.
Although a lot of countries have letters on their number keypads, they are only just catching on to this idea in the UK. Therefore, don't just remember the word that signifies your PIN; rather, remember the finger movement pattern. Also, try to familiarize yourself with UK money before you arrive in London.
Cash and Credit Cards
You will always need cash as well, to pay for the tube or a cup of coffee.
The best way to deal with UK currency is to simply bring your ATM card for withdrawing cash, and use your credit card for Chip and PIN purchases. That way, you get the best exchange rate of the day, don't need to carry large amounts of cash, and your purchases are most likely insured as well (depending on your credit card company).
Main "High Street" Banks
Traveler's checks are a safe form of currency to carry. Buy UK pounds sterling traveler's checks before coming to London as fees will be incurred to exchange other currency traveler's checks.