Have you considered this one? He's few years older but the only William Fitzgerald in Oswestry in 1841
HO107/915/7/4/1
Willow Street, Oswestry
May or Mary Fitzgerald, 45
Samuel, 20, Attornies (sic) Clerk
William, 15
Joseph, 12
All b. County except May/Mary
Apart from a Sarah at HO107/915/7/13/18, this is the only family of Fitzgeralds in Oswestry in 1841