london public bus-best for cheap tour

Elaine, I think what you're looking for is the No 11 London bus, Catch it outside Victoria Train station going towards St. Pauls. Go upstairs and get as near to the front as you can.
There's another good route, the 139 that goes from Waterloo to Baker Street and goes through Haymarket, Regent Street and part of Oxford St.

Probably not. Buses can't go around the Victoria Memorial loop, so all you could do is pass along the side at about Birdcage and try to get a glimpse down the side which shows nothing but fence and a linear view of the front façade. I might be wrong and the limitation is just on tour buses, but a taxi can go anywhere. The other thing I can't picture is why one bus would pass all those things - - it's illogical. The rest of your stuff is clumped and not far away. Maybe tube yourself to Westminster and get a taxi to make a loop and toss in a couple of other things to make it worth his time. The problem is that I can't picture where the closest taxi rank is a you come out of Westminster. Edit: Or just do what Maggie says.

The number 24 goes through Victoria to Westminster, then along Whitehall to Trafalgar Square and on and on to Hampstead Heath. But that's just one example of the many interesting routes around central London, so take a look at this map which shows many more: Key bus routes in central London
I think that should give you some other ideas.

Ed is right by the way, no buses go round the front of Buckingham Palace, but a good few services run along Grosvenor Place, which is at the back of Buckingham Palace Gardens, so from the top deck you may get a glimpse over the wall. Distant views of HMQ walking the Corgis may be too much to hope for though...

The Transport for London website has a downloadable PDF guide called "Welcome to London: Information to start your visit." It contains Tube and bus maps, including one map showing key bus routes in central London with icons identifying the location of popular tourist attractions. Here is the link to the guide.

The map that I linked to (and which I see Tim has subsequently mentioned) shows you the main sights that various bus routes go past, but for a different and very entertaining view I recommend the following website: London buses: One bus at a time It's a blog about a project started in 2009 by a number of retired women in London (the "Ladies who bus"), to ride every London bus route from end to end, starting with the number 1. By February 2013 they had got as far as number 607 and started on the unusual route numbers, A10, B40 and so on, and by Tuesday this week they had got to route H12. Each bus trip has a full description of what they saw including places of interest, with photos. For example, here are the routes that Maggie and I suggested: 11 24 139

great info--tx! Also, I saw that Rick Steves book has a very good map/description.