Colin, if you buy the marriage cert which Len referred you to (along with the 1851 census on which he based the information) the cert will give you his father's name and occupation - which is far preferable to guessing which IOM Ushers were his relatives. It will also confirm that "Levi Usher a Servant" was given as his father in an official record, given by Henry himself - or is this certified marriage where you got his father's name from?

Marriages Dec quarter 1842
Surname First name(s) District Vol Page
Usher Henry Liverpool 20 168
Cottrell Maria Liverpool 20 168

GRO online with a credit card:
www.gro.gov.uk/gro/content/certificates/

Or order from the local RO:
www.lancashirebmd.org.uk/

Sue