Thank you Emms & Patrish - I really appreciate your help
I am not 'convinced' he was born in Carlisle / Cumberland - but that is what is noted in the 1861 census, so I thought it might be worth checking... To be honest, I'm floundering a bit in the dark with this one! After William reached London, all subsequent Santons in the line I'm tracing were born in London area. I know that Yorkshire is a Santon 'hotspot' going back hundreds of years - but getting past William is a bit tricky at present!
Anyway, thanks for the help and suggestions.
Best wishes,
Tim