Agree Back King Street.
There was this note in the 1841 CENSUS for Great Bolton:
Folio 41 - 55
John Lomax - Enumerator - Enumeration District 12
Thomas Balshaw - Registrar
All that part of the township of Great Bolton which lies north of Deansgate comprising Simpson Square, Grime Street, Back King Street, south-west side of King Street, Waterside, Joiner's Square, stop at the Bridge St shop, and north side of Deansgate from Simpson Square to King Street.