Hi 7/3,
Thanks very much for the info. My Robert and Margaret did have a son called Robert but according to the census info he was born c1820 and was one of eleven children, of which two of them were born before him - Samuel Clinton c1811 and Jane Clinton c1816. I guess they may have had three children out of wedlock but I don't know. It's a shame I cannot obtain a marriage certificate for Robert and Margaret to know her surname for certain. Unfortunately, the bmd records on Ancestry and Findmypast.com only start from 1835.
If you have any more ideas on how to find out for certain, please let me know.
Winnie the pooh