money for various countries

London-uses the pound sterling (not euro)

Amsterdam, Paris, Germany, and Italy-yes

Switzerland-uses the Swiss Franc

And no, they do not accept payments in Euro in the UK nor in Switzerland. And no, they do not accept payments in any other currency in France, the Netherlands and Germany. You will have to get all three currencies - ideally you withdraw cash via your debit card in the respective countries. Your own bank may be able to provide you with a list of European partner banks. Alternatively Bank of America allows you to withdraw cash in Germany, France and the UK at certain ATMs free of charge.

You'll find excellent information elsewhere on this site, and even more in the books. Start reading, and come back if you have more questions. You can also read earlier forum posts. This site is a great resource.

Lets focus on the best way to pay during your trip, with your credit card. Many cards do not have international transaction fees, provide the best currency exchange rate and are accepted throughout Europe.
Be aware NOT to accept what is called a Dynamic Conversion Rate which some vendors will try and advocate as being "better for you." DCR is where a vendor receives a financial incentive to have you agree to pay your bill at the currency conversion rate offered by the vendors third party money exchange provider. When presented with the bill and a offer to use the DCR, ALWAYS decline the offer. If a vendor says it is required by: your credit card company, the law or whatever other bogus excuse; INSIST that you will not do so.
Check with your bank to learn if your debit card works in Europe (most do) and for what transaction fee (many are at 3%) and use your card at an ATM machine to obtain cash. We seek to use ATM's located outside of tourist zones (less probability of pick pockets seeing you obtain cash from the ATM) and we only take out relatively small amounts of cash (about $200).
During the decades of traveling in Europe we have dramatically reduced the amount of cash we convert and carry. For a recent 14 day trip we only converted $500 into euros. Another reason not to convert large sums of cash is to reduce exposure to pickpockets. Please do read on the RS site the actions you should take as precautions against pickpockets, but do not become paranoid over this issue.

I disagree with using credit cards for everything in Europe, or specifically, in Germany.

The small Mom & Pop Pensionen, Zimmer, etc, that make the trip so culturally rich, don't usually take credit cards, and they are less expensive than places that do take plastic. I normally spend about 30€ per night for a single room with breakfast. That would be difficult to do without paying cash.

I also eat well on an average of about 20€ per day, not including breakfast, which is included in the price of the room. Usually at least one meal is a sit down meal, although I often grab a sandwich and drink at the train station when on the go. I don't check to see if they accept credit cards, because I don't use them, but I've never notice a CC sign in the window and my feeling is that these small places don't take them.

When you pay with cash, you don't have to worry about someone trying to force DCC on you.

Another reason not to use credit cards is that too many people have reported receiving charges from places like Croatia months after using a credit card for dinner in, say, Paris.

I have an ATM card that gives me two fee-less withdrawals per calendar month (four for a trip that spans two months) and another that only charges 1%.

In my experience, Europe is more of a cash society then the United States (if that's where you're from), although that may be changing. In any case, I would plan to use cash for most transactions unless you're buying something really expensive.

Credit card fraud is far more of a risk in the USA than Europe - approximately half of the world's card present fraud occurs there now mainly because of the lax security at the point of sale (obsolete mag stripe/sig based cards).

Acceptability of cards do vary across Europe but even hitherto backward areas such as Germany are being dragged on these days.