I’ve now checked the 1851 census for a Hewes family in Colchester. At a household at 14 Eld Lane we find:

Margaret Greggs, Head, Widow, Female, 62, Nurse. Almswoman, Essex West Bergholt
Emma Hewes, Daughter, Married, Female, 30, Bakery Wife, Essex Colchester
Emma Hewes Jr, Grand daughter, Female, Unmarried, 6, Scholar, Essex Colchester
Isabella Hewes, Grand daughter, Female, Unmarried, 4, Scholar, Essex Colchester
Henry W. Hewes, Grand son, Male, Unmarried, 3, Scholar, Essex Colchester
William I. Hewes, Grand son, Male, Unmarried, 1, At home, Essex Colchester

This definitely matches very well, however it seems that Emma’s maiden name might be Greggs rather than Griggs. FreeBMD shows no Greggs/Hughes marriages at all. There’s a birth registration for an Emily Hewes in Colchester in December quarter 1844, but no births for Emma Hewes anywhere in the approximate time range. FreeBMD doesn’t show a death for a Margaret Griggs/Greggs of the right age in the right area to give a clue as to which might be right. FreeBMD tells us that Henry W. is Henry Walter.

I can’t find a Henry Hewes in the 1851 census that looks as though he is the husband of this family. Presumably he is still alive at this point as Emma’s condition is reported as married, rather than a widow.

I’ve ordered birth certificates for the birth of John Hughes registered in Reading in the September quarter of 1856, and the birth of Margaret Hughes registered in the March quarter of 1859. If Margaret was born in 1859 she would have been 2 in 1861. I can find no trace of her in the 1861 census. This is a bit of a puzzle.