Why, oh why do people take Dickens' writings as being about "Victorian" London?
Generally speaking Dickens based his writings on his own childhood which predated Victoria's accession to the throne by some years.
With regards to the writings of Henry Mayhew, I note his book was published in 1861 when many the much needed reforms to aleviate the abuses of the time were already in force, the various Factories Acts and other early health and safety legislation being typical examples.
Granted, Dickens' writings did assist in making people aware of the abuses of the time and helped speed up the introduction of similar legislation, but by the 1850's the ball of reform was already rolling and gathering momentum.