Although I don't always like to be the typical tourist, I really did enjoy the hop-on hop-off tourist buses in London. You don't really get outside of the city center, but the guides are very friendly, you get to look at things as you travel from sight to sight (instead of emerging from a tube station like a gopher all discombobulated), and you get running commentary and pass things you may not have known you wanted to see. The buses will serve all of the places on your list, but it's true thay might take a little longer to get from place to place due to frequent stops and traffic, but I found that after a day on the bus I was much better able to find my own way along the winding streets of London AND understand where I was for the most part when I exited a tube station. You are perfectly able to go inside Westminster Abbey etc. while using the buses. Since a lot of your destinations are pretty far away from each other, it's a great way to get the "long and winding road" experience and still get from place to place pretty effectively. Most of the buses also include a short cruise on the Thames (perfect photo op).