Thank you also Capetown.
William Butcher married his second wife Sarah in Calne in February 1828. I think his first wife, Anne, died in 1827 leaving him with, I thought two children, but from this very helpful thread, possibly it was four children.
Little wonder that he married again fairly quickly!
The odd thing is Sarah's age. The Census report of 1851 says she was born in Melksham in 1783, which would make her 10 years older than her husband William, but when Sarah died the following year, in October 1852, her stepdaughter Elizabeth Morley (William's married daughter) gives her age as 77 years, which would give a birth year of 1775, and make Sarah 18 years older than her husband William.
Elizabeth was in a position to know as William and Sarah were living with the Morleys by then.
Sarah's death certificate records the main cause of death as "paralysis - 10 years", so I assume life wasn't easy.
William continued to live as a lodger with the Morley family in Calne until he died in 1873.
Again my thanks to all who have responded to my original post.