Hi to abergynolwyn and Ermintrude46 . I have only just accessed the Rootschat website after a long absence so I hope you will not mind the joint thankyou letter. Somehow I could not find the link to reply to you individually.
The superannuated shipwright is my ancestor and it delighted me to find some extra information after several years fruitless searching.
Some very kind people in Pembrokeshire have sent me details of Thomas Harrison from the excellent book called Pembrokeshire People by Richard Rose and I was also able to read the book at my main library and gain a few more facts about the extended family. This does not reduce my gratitude to the people who have taken time to help me, so please accept a big thank you.

The idea to search in Hampshire rather than Durham for background information on Thomas Harrison is an excellent idea, one which I will certainly follow up.
I intend to search in the Access 2 Archives for the other information suggested by Ermintrude 46. together with a search in the Greenwich Pensioners site. Luckily I have 1841 and 1851 census details of Thomas and his family in Pembrokeshire but the place of birth is so vague I was really struggling to go further back. Now maybe I have the end of thread that will slowly unravel the next generation Of the Harrison Family.
Many many thanks,
Irene