Gentlemen,
Thank you for your responses; according to Nigel Calder - Boatowner's Mech & Elec Manual- "in normal use shuts off the water in the seal altogether" & is apparently composed of shredded teflon in a heavy hydrocarbon base. Please note I am quoting & make no claims in respect of understanding!
"Drip-Free Packing" as made by The Drip-Free Packing Company of Florida. There was a thread on sourcing it in the UK last year, concluded that no uk suppliers, and that West were best bet.