As the photos show, the service was operated by SK61s. Callsign Northbound was 'Link1' and Southbound 'Link2'. British Airways Helicopters had a base at Gatwick, near to the old 'Beehive' terminal. The service connecting G'wick and H'row was still running in the early 80s. I believe that for passengers interlining between the two Airports, the air fares were inclusive of the helo transfer.