I thought Faststream was only involved with Cruise and Commercial vessels, not Yachts?
Since the flag is UK proper,(not IOM, Bermuda or Gibraltar etc.) that limit the options considerably, for Master at least. Unless the rules for Yachts are different?
There are several Crewing Agents that specialize in Yachts, both for private and commercial charter purposes, but if Polar endorsement is required the pool is probably limited: http://www.acronautic.com/crew-agencies/