Surely the starting point is somewhere on the east coast of Dear Old Blighty
"..down by the lower Hope dear lass
With the Gunfleet sands in view.."
and
"Fly forward, oh my heart
From the Foreland to the Start..
I'm under the impression that Lower Hope is a reference to Hope Reach in the Thames estuary. Gunfleet Sands are in the North Sea near Clacton-on-Sea, the Forelands are in Kent, and Start Point is in Devon so, without the benefit of a short-cut via the Panama Cana,l Kipling's directions would be correct. You'd either have to sail south-west to Cape Horn and then north to San Francisco, or east via the Med and Suez Canal and onwards across the Pacific. IIRC the preferred route to SF in the early years of the C20th was via Suez and the Indian and Pacific Oceans