There are a wide range of Classes of exemption that are coded A through to W. Many of them are pretty obscure and don't apply to the average man in the street. These are definitely fixed across the whole country and are part of the legal framework under which Council Tax was introduced.
The following link explains the different exemption classes (I took it from Westminster City Council for convenience - but it is the same across the country)
http://www.westminster.gov.uk/councilgovernmen tanddemocracy/councils/counciltaxandfinance/no tes.cfm
As far as I can establish, councils do have some local jurisdiction over how much %age reduction to give for various exemptions. This may explain why different folks are coming back with different answers.
Carron - the main Classes you should be interested in are Class A and C. Ask Fife exactly what they give in discount for both of these Classes of Exemption.