You do not need to provide a letter, there is a section in the form which they need to fill in.

E Fidan
Administrator

Hello All,

Do the referees need to write a letter and/or do they just have to fill up the form? Does anybody here know?

Thanks,

Venus

Letter from referee is not required. They
will sign the original form and there are conditions imposed on the referee
also.  SO please make sure you know those conditions.  They need to
provide the Passport information also and their contact so if Home office needs
to they can contact the referee.

You need to go to these Web sites to get complete
information

http://www.ind.homeoffice.gov.uk/ind/en/home/applying/british_nationality.html

http://www.ind.homeoffice.gov.uk/ind/en/home/applying/application_form.html?