does anyone know of a george thomas thompson born 1883?

There are four possible entries in the birth indexes for George Thomas Thompson in 1883, all in the south of England. There are two in Lancashire in 1884. http://freebmd.rootsweb.com/cgi/search.pl

Have you obtained his marriage certificate? I have seen the name of the ship included in the occupation field in some marriage certificates.

If you know the name of the ship, you can search the Crew List which will tell you your great grandfather's year and place of birth, amongst other things. 10% of the Crew Lists are held at the National Archives at Kew:-

http://www.nationalarchives.gov.uk/catalogue/RdLea...

The National Maritime Museum at Greenwich took a further 10%:-

http://www.nmm.ac.uk/

Some went to County Record Offices, and approximately 70% of the Crew Lists went to the Maritime History Archive in Newfoundland, Canada:- http://www.mun.ca/mha/

Unfortunately you need to know the name or official number of the ship in order to search for a crew member.

Have you searched for your great grandfather in the 1891 and 1901 census returns? http://www.nationalarchives.gov.uk/census/default....

If you order his wedding cert it should say who his dad is which may help you find him on the 1901 or 1891 census.

Did he marry Margret Maud Gregson in Preston 1908?

http://www.freebmd.org.uk/cgi/search.pl

Looking for a George Thompson is a real needle in a haystack job :)

you should go on "who do you think you are".