Blake wrote the poem The Chimney Sweeper about boys sold into the trade long before the 1850s and Elizabeth Barrett Browning published The Cry of the Children in Blackwood's magazine in 1843. Charles Kingsley used his The Water Babies to question child labour and England's treatment of the poor in general in 1862-3.
No one with any pretensions to knowledge of those times can claim not to know about child labour.