The fee from the UKBA link states £851 includes the ceremony fee
http://www.ukba.homeoffice.gov.uk/sitecontent/documents/britishcitizenship/nationality-fees.pdf
The overall fee for British citizenship comprises two elements. They are:
a) Fee for handling and processing the application. None of this is refundable if the application is refused or withdrawn.
b) Citizenship ceremony fee. This is paid by applicants who are required to attend a citizenship ceremony. It is refunded to applicants whose applications are refused or withdrawn.