Have you eliminated these as possible candidates for William Leigh in Leyland on 1841 census ?
William Lee. weaver, bachelor of Leyland married Elizabeth Mackral at St. Andrew, Leyland 1820;
William Leigh, weaver, widower of Leyland married Ann Gregson at St. Andrew, Leyland 1821.
William Leigh, weaver, widower of Leyland married Jane Platt at St. Andrew, Leyland 1835;
(Lancashire Online Parish Clerks)
Other men in Preston area named William Leigh/Lee/Lea included:
William Lee, bachelor, Manchester who married Ann Davidson at St. John, Preston 1835.