I agree Stu, expensive. But I notice everything is expensive now. When I went to London at christmas - same thing. Madam Tussauds, London Eye - similarly expensive.
The other thing I noticed was how many foreign tourists there. Huge parties of french students / school kids etc.
Cadbury World. If you go on Thursday (Purple Thursday) you can buy one and get one free i.e. £14.75 for two adults.