William Williams

This is my first post, so I hope I'm doing it right!
I need to know where William Williams was in 1848-1855
I can't find him in the 1851 census or any reference to him during that period.
William was born around 1808 in Llandegla, North Wales
He moved to London before 1828
In 1828 he married Mary Douglas from Gainsborough
In 1929 they has a son Thomas Robinson Williams
Mary died in 1832
By 1841 (in the census) he'd remarried an Ann Knight
I can't find the marriage but would love to
They lived at 21, Harp Alley, St. Brides, London
They had children:
Mary Ann b 1837
Elizabeth b1839
Jonathan b 1840
Hugh b1842
Frederick b1846
Eliza Mary b 1848
William Henry b 1857
I can't find any children 1848-1855 or find William Williams during that time either
I've found him in an 1856 London Trade book
William was a hairdresser
Please can anyone help me?
Thanks in advance