GReat records
http://www.lan-opc.org.uk/Below are the two John's who may be the right John, the Trees on Ancestry favour the b1801 John but Maggy who has posted above puts a strong case for the John who was baptised in Jan 1799
Baptism: 12 Jan 1799 St Michael, Cockerham, Lancashire, England
John Lamb - Son of Richard Lamb
Occupation: Cordwinder
Register: Baptisms 1793 - 1812, Page 15, Entry 2
Source: LDS Film 1278859
Baptism: 30 Aug 1801 St Michael, Cockerham, Lancashire, England
John Lamb - Son of John Lamb & Elizabeth
Abode: Glasson
Register: Baptisms 1793 - 1812, Page 22, Entry 28
Source: LDS Film 1278859
Record for Ann Threlfall
Baptism: 5 Sep 1802 St Michael, Cockerham, Lancashire, England
Ann Threlfall - Daughter of Richd. Threlfall & Betty
Born: 14 Aug 1802
Abode: Forton
Register: Baptisms 1793 - 1812, Page 27, Entry 10
Source: LDS Film 1278859
Marriage of John and Ann
Year:1825
Supplied Surname:THRELFALL
Surname:THRELFALL
Full First name:Anne
Supplied First Name:An
Spouse Surname:LAMB
Spouse Full First name:John
Spouse First Name:Jn
Place:COCKERHAM
County:Lancashire
Record source:Boyd's Marriage Index 1538-1840
Data provider:Society of Genealogists
If you PM me with your e-mail address I'll send you my take on the family tree which I have put together using Microsoft Excel