Hello Helen,
If you search the IGI for Clayton with Frickley, surname Harrison, parents William and Alice, it comes up with the following baptisms:
Edward Harrisen, born 4 Jan 1800, bap. 2 Feb 1800
George Harrison, born 18 Dec 1802, bap 9 Jan 1803
Mary Harrison, born 16 Mar 1805, bap 14 Apr 1805
Hannah Harrison, born 9 Jun 1807, bap 28 Jun 1807
William Harrison, born 25 Mar 1809, bap 16 Apr 1809
Robert Harrison, born 9 Jun 1810, bap 1 Jul 1810
(All extracted records - Batch no P007561)
It would look like either your William is not as old as he claims on the census, or you may need to look for different parents (or they moved away from this parish? ).
Other Williams listed for Clayton with Frickley are:
William Harrison bap 24 Nov 1776 father George
William Harrison bap 31 Jul 1796 parents Thomas & Martha
Hope this helps, let me know if I can help further,
Sally
