Southall is part of the borough of Ealing.
The 33 divisions of the London Urban Area - City of London (officially not a borough), City of Westminster, Kensington and Chelsea, Hammersmith and Fulham, Wandsworth, Lambeth, Southwark, Tower...
Southall is a suburb in the London Borough of Ealing in West London, anout 11 miles from the city centre.
Croydon is the biggest borough by population and Bromley is the biggest borough by area.
There are 32 boroughs of London.