Morning Bob, thanks for your swift reply.
What I have is the baptism of my 2 x great grandfather William Johnson at Stepney in 1803 who became a Hemp Dresser like his father Joseph; a Ropemaker and 2 Twine spinners all Johnson close in age to Joseph at Portsmouth Dockyard in 1806 and the Ropemaker alone at Chatham Dockyard in 1808. There is also another Johnson Hemp Dresser, again close in age to Joseph (different family but perhaps linked) who was at Mile End in 1803, Portsmouth in 1806, Chatham in 1808 and Great Yarmouth in 1820.
These snapshots are all I have at present and there may have been greater mobility than appears from surviving Admiralty records. This is not like Gypsies and Circus folk moving frequently from place to place so the question is: Is this degree of mobility suitable for inclusion in the Travelling People database and discussion on the Travelling People Board or should I be using other boards?