Trim's right--IMIS is a very good broker. I've used them in the past, and have heard great things from folks that were insured through them when Hurricane Ivan hit Grenada.
In London, you might try Besso, Ltd. They offer policies underwritten by T. L. Dallas. I'm with them right now. Quentin Brooksbank is the broker that I deal with.
Besso Limited 8-11 Crescent, London EC3N 2LY Tel No. +44 (0) 207 480 1125 Fax No +44 (0) 207 480 1272 Website: www.besso.co.uk
I don't know about coverage in the Pacific, but both offer U.S. and Caribbean coverage.