Developer Finance. - Public forum - Planning Advisory Service (PAS)

A typical development appraisal will factor into its assumptions the costs of developer finance (borrowing). Can anybody signpost me to an independant source where typical rates can be obtained? Obviously the lending rates will vary between developers and even between different sites, but there must be somewhere to get an 'average rate'? Are these rates linked to base rates, and if so, how? Thanks in advance.