Your enquiry appears to relate to the Dept of Africa, Oceaia and the Americas: General contact:

ethnography@thebritishmuseum.ac.uk

by phone:
+44 (0)20 7323 8041

by post:
Department of Africa, Oceania and the Americas
The British Museum
Great Russell Street
London WC1B 3DG

There is a staff list at:
http://www.thebritishmuseum.ac.uk/ethno/ethcost.html

and some FAQ which might help (incl about looking at artefacts not on display) at:

http://www.thebritishmuseum.ac.uk/ethno/ethcofaq.html

Hope that is useful - info was all on website - just a matter of prowling until you find it!