Alliance and Leicester sold off a huge part of their ATM network. This is the kind of thing I’m talking about - I can’t really give any guidelines to foreigners that won’t be stupidly long, but looking for that charge will, I think, be pretty reliable.
Alternatively, I actually know Central London very well. Most of the time I try to live in Scotland, but when I’m not then I live in Greenwich and know most of the centre - I could probably help a doper find a cash machine next to any tube station in zone 1. But not in a timely fashion one suspects!
Just a little aside: whatever cash (euros, pounds) you have at the end of the trip, try to exchange them before you get back to the US. Since US banks do so little currency exchange, you’re get a hefty processing fee added on.
My wife and I stashed a $10 Canadian note on our trip to the Montreal casino, so that we’d have guarenteed cab fare back to the hotel. We ended up not needing it, and forgot about the $10.
Back in DC, I went to a bank to ask about exchanging it. Besides getting a really shitty exchange rate, they wanted to charge me $5 USD, so I would’ve only got $1.50 back. I ended up keeping it in my wallet for the last 14 years.
You’re referring to Canadian $1 and $2 bills. They are not worthless; they remain legal tender for their face value, though it is rare to see them in circulation. From the Bank of Canada website on the 1986 banknote series:
Check out the specific fees on your ATM card and credit cards. Some do not charge fees for using them to pay but do charge for using them in an “out of network” ATM.
Make sure that you carry a MasterCard or, even better, Visa. Many credit card companies which are popular in the US are very limited or unknown in Europe.
