London trip- cash to carry

All the attractions, restaurants, and grocery stores we went to in London took our credit cards. We very rarely spent cash while we were in London. Many museums in London are free, so you won't be needing cash there. The cafes or cafeterias in the museums take credit cards for your lunch or afternoon coffee.

The machines from which you purchase the Oyster Card all take a credit card.

Some black cabs in London will take your credit card, however, some want cash.

Hop-On-Hop-Off bus tour companies will take your credit card.

For just three days, you may need no cash. You could take about 300 pounds if it makes you feel more comfortable.

If you like to pay cash for everything, 100 pounds per day will be enough, especially if you travel frugally.

Where will you be going after London? If you will be traveling out into the English countryside, train tickets can be purchased with your credit card.

I'm somdone who prefers cash to credit so I can better track my spending. I add up the cost of any sites/activities that I plan to do and have that amount on hand, plus whatever I think I will spend on food. I'm not into food tourism, so I will eat whatever sounds good when I get hungry, so that saves me money.

I do budget for items I may come across that I want to purchase, but it's usually thing like kitchen towels and mugs and books. I did buy myself a new set of flatware, but that went on the credit card.
Oyster card will be £5 deposit plus £25 for 3 days. You can get a refund on the deposit and remaining balance at one of the Heathrow tube stations before you leave, but I don't think you can at Gatwick.

Most places do indeed take credit cards, but there are some places - street markets, some out of the way shops and restaurants - where you'll do better to have some cash. That said, 300 pounds is a lot for three days, even if you're paying cash for everything.

If it were me - and I'm somebody who's happy to put most purchases on a credit card - I'd withdraw 40-50 pounds from an ATM upon arrival. At first, I'd use it only when I needed to, but if day 3 was approaching and I hadn't spent it yet, I'd start paying cash even at places that take credit cards.

Admission to some sights can be expensive. Admission to Westminster Abbey is £20 for adults.
To St. Paul's Cathedral, £18.00 per adult. Fast-track tickets for the London Eye, £27.50.
So, if you did all three of these activities in one day, plus food, you would soon reach £100. in one day.

Big Bus 24 Hour Tour - £26.
http://eng.bigbustours.com/london/home.html
Visit the Tower of London, price £25.00 per adult.
This takes half of your £100. in one day, before you've added in your food for the day and one cab ride.

So....£100. per day is not an outrageous amount to take. London can be expensive.

Make a list of the sights you wish to see, with their cost, so that you can budget for these attractions. Especially if you are wanting to pay cash for everything.

You will want to arrive at some combination of free sights and some pay-to-see sights. You can pick up a copy of Rick Steves' London guidebook at your local library to help you decide, and make up your itinerary.

As I said before, there are many free sights, so take advantage of those!

But like you said, there are many great things to do in London that cost nothing at all, so I'm not sure it necessarily makes sense to pack your schedule so full of expensive attractions. And even if you do, most of them take credit cards.

We spent a week in London in June before flying on to Lisbon for a RS tour. We used his London guide book extensively for sightseeing, hotel, and eating. In our 14 years of going to Europe we seldom use a credit card except to pay for hotels or major purchases like a rug from Turkey. We much prefer to use local currency that we get using a debit card from an ATM machine. We ate at several mid to low priced places that we found in the RS guide book and were never disappointed. We do not take any European local currency with us from the US preferring to get it from ATM machines that are all over the place these days. We just make sure to use ATMs that are NOT connected to one of those currency exchange rip-off companies. I always look for ones that have the symbol of the network my debit card works with. Happy travels

I went to London in June for 5 days and spent about 60 pounds a day or less. Mind you, that I prepaid for all my tours, my hotel, etc. The only items I paid for were lunch and dinner, Oyster Card and souvenirs. I was very frugal on this trip since I was travelling solo and found it very easy spend little throughout the day.