We have an alternative solution!
Some Londoners report that they have spotted Google-logo cars with big cameras on their tops cruising London streets these months. But if you logged in Google maps, you'll notice that there are no Streetview for London yet!
Don't worry, there's Seety.co.uk! A site offering exclusively street views for London with an interface similar to Google's. Just double click on the point of the map where you want to see a street level view and a small window will pop up offering you the requested street view.
A street-view from the middle of Westminster bridge: