Before going to London the first week of April (4/1 to 4/10) I did a lot of reading and viewing of Rick Steves material on the site. I also purchased the London guidebook and poured through it for ideas and for creating my adventurous plan. I decided to go with a B&B, and and researched several online that the guidebook had mentioned. I ended up staying at the St. David's Hotels for my entire stay and it worked out very well indeed. The B&B staff were very friendly and helpful, and the included breakfast was a great starter. The B&B also had a great location, just some two blocks from the Paddington Tube entrance and the Paddington Train Station. Another helpful suggestion from the guidebook was to use the Oyster Card for Tube/Bus. I got mine from a store near the hotel and applied a 7-day Travel Card to it. I never worried again about fares to get around. For the three days remaining I just added another 20 pounds and it came out fine.
If you're going to London for the first time (or anytime) I can't recommend highly enough using the Tube (underground trains). I confess I was pretty confused the first day and a half, but it then came together for me and I got very comfortable with it as my primary mode of transportation. I used a bus a total of three times when in England, and the only time I preferred it was when it was in a rural area outside of London. Otherwise, in the city buses have to fight traffic, and your driver may not give a hoot about how nice the ride is. By comparison, the Tube is consistent and relatively smooth going. I prefer it by far (except for all the steps! LoL). Two apps on my smartphone helped me very much - the "Tube Map" and the "Tube Tamer." The Tube Tamer is pure gold for getting around London by the Tube (even bus). You just input your starting location (I was able to enter "St. David's Hotels") and your end location (e.g., Tower Hill) and the app tells you just which trains you need to take, along with instructions on when/where to change, and it even helps you with walking instructions, providing a live map view that you can use to navigate to your destination. Don't miss this app (Tube Tamer)!
There were a number of times I was able to use Apple Pay on my smartphone for purchases (even for taxi and trains), but otherwise I just used my bank card if needed. Mostly though, I used cash. When I got to Paddington station from Heathrow I noticed a cash machine, and I just drew out about 300 pounds to get started with. Toward the end of the trip I took out a couple hundred more. So, normally I used British currency for purchases. I read someplace about the new polymer 5 pound note with Churchill on it, and hung onto them when I got them to give to family members/units when I got home.
Another helpful suggestion from the RS guidebook was the Big Bus tours. I purchased my tickets online before leaving and it worked out fine. It's really a great way of getting acclimated to a new city or place. Otherwise, you just muddle around trying to find your way, wasting valuable time. So, I made the bus tour my first activity and it helped immensely. I did a one-day trip to Paris on my last full day, and I took the Big Bus tour there also. It provided me with the opportunity to take lots of pictures of Paris from the open-air top, which I could never have gotten just fumbling around by myself.
Highlights: Buckingham Palace square and the park nearby; the London Eye (great views and great to take pictures of too); Tower Bridge (its iconic, one of a kind); the British Library (treasures room); the National Gallery; Churchill War Rooms; Parliament; the Crown Jewels (the Tower); and so much more.
Here are my snapshots of London and Paris. Hope you enjoy!