Thank you very much for such a detailed response!
My friend has been leaning towards Bonfield's death as 1849. This could well be Sarah and William on the census, although William was born in Westminster? However I shall recommend it to my friend and we shall look into it.
Unfortunately it looks like Sophia did indeed die, but which Sarah was her mother? I suggested the possibility of Sophia being born out of wedlock to Sarah Shelton, as her parents got married later in the year, and that's the reason she was born in a lying-in hospital?
Was the other Bonfield 63? This could shed light on another Bonfield Bryant!
Thank you very much! Unfortunately my friend cannot find a marriage for Thomas and Alice, however we believe that Thomas re-married twice and is found living in Bedford on censuses born 1784 in Little Paxton. This would make him extremely young when he married Alice (if he even did!) but the census could be a couple of years out! However there are no births for Thomas in Little Paxton.
Earliest known record of 'bonfield' in Bryant is Robert Bonefield Bryant in 1737.
There was also a Bonfield Bryant who was married to a Grace (will records).
There are so many Bonfields!