I searched for your relative's birth.

There is a Mary Ann Sutton registered 1855 in Greenwich under the BMD listings. I searched to see if she was christened/baptised but unless her father's middle name was George it looks like you might have to obtain the birth certificate yourself.

I found two christenings for a William Sutton in Hitchin:

1825- William and Sarah

1823- William and Caroline



Hope this could help at all