Len (and Kim),
Thanks for your very interesting and useful response. I am afraid the dob for Margaret that I posted was a typo and should have read circa 1789 which would make her marriage in 1811 possible but still does not tie in with her age on the 1851 census. I am trying to think where I got the suggested d'sob for both Thomas and Margaret from - and my notes don't tell me - tut tut - I really must make note of sources...
I had the burial of Thomas in 1843 but did not realise he was listed as being 73 at death which would mean a dob of around 1770 rather than 1788......
I had found the various IGI entries for their children - it is Daniel who is my direct ancestor so he ties up in both in the 1851 census and the IGI entries.
I see as I am typing this that Kim has posted the 1841 census - which is great and ties in with the Thomas buried in 1843.
Must now sit and think and see how it all fits together.
Are the parish records for Baptisms, Marriages and Burials available for the island?
Cheers and thanks