In 1790, William was from Great Sankey when married Sarah at Prescot.  There is only one Warrington or Prescot baptism and that is for William son of Ralph a potter and Ann of Prescot.  However, that William also became a potter and married Mary Denton in 1788 at Prescot.

Baptism: 14 Apr 1775 St Elphin, Warrington, Lancashire
Wm. Mather - Son of Jno. Warburton & Martha Mather, Spinr.
    Occupation: Husbn.
    Notes: Illige.
    Register: Baptisms 1760 - 1781, Page 137, Entry 19
    Source: LDS Film 1562957

or

Name    William Mather
Gender    Male
Record Type    Baptism
Baptism Date    29 Jun 1760
Baptism Place    Grappenhall, St. Wilfrid, England
Father    John Mather
Description    Grappenhall, St. Wilfrid. BMB
Abode    Chelwall, Weaver

or

Possibly the son of Isaac Mather of Warrington who was a joiner

Possibly died Latchford, Warrington Feb 1826, aged 53 (born 1773) or Tilley Street, Warrington Feb 1838, aged 67 (born 1771)

Baptism: 18 Apr 1779 St Elphin, Warrington, Lancashire
Elizth. Percevall - Daughter of Thos. Percevall & Ann
    Occupation: B. Smith
    Register: Baptisms 1760 - 1781, Page 174, Entry 9
    Source: LDS Film 1562957

7y 8m when died (but probably should be 2y 8mo)

Baptism: 23 Aug 1807 St Elphin, Warrington, Lancashire
Peter Mather - Son of William Mather & Elizabeth
    Occupation: Cabinet Maker
    Register: Baptisms 1781 - 1812, Page 296, Entry 10576
    Source: LDS Film 1562957

Name    Peter Mather
Baptism Date    23 Aug 1807
Parish    Warrington, Lancashire, England
Father's Name    William Mather
Mother's Name    Elizabeth Mather
Register Type    Bishops Transcripts
Reference Number    Drl/2/468

Burial: 26 Apr 1810 St Elphin, Warrington, Lancashire
Peter Mather - Son of William Mather
    Age: 7Yrs 8m
    Occupation: Cabinet Maker
    Register: Burials 1779 - 1812, Page 262, Entry 22
    Source: LDS Film 1562958

Baptism: 26 Apr 1810 St Elphin, Warrington, Lancashire
Mary Mather - Daur of William Mather & Elizabeth
    Occupation: Cabinet Maker
    Register: Baptisms 1781 - 1812, Page 329, Entry 11834
    Source: LDS Film 1562957

Name    Mary Mather
Baptism Date    26 Apr 1810
Parish    Warrington, Lancashire, England
Father's Name    William Mather
Mother's Name    Elizabeth Mather
Register Type    Bishops Transcripts
Reference Number    Drl/2/469

Mary was baptised the same day her baby brother Peter was buried.

Name    Eliza Mather
Baptism Date    10 May 1812
Parish    Warrington, Lancashire, England
Father's Name    William Mather
Mother's Name    Elizabeth Mather
Register Type    Bishops Transcripts
Reference Number    Drl/2/469

Eliza Daughter of William Mather Cabinet Maker and ELizabeth his Wife

Baptism: 24 Apr 1814 St Elphin, Warrington, Lancashire
Peter Mather - Son of William Mather & Elizabeth
    Abode: Dolmans Lane
    Occupation: Cabinet Maker
    Baptised By: J Topping Curate
    Register: Baptisms 1813 - 1818, Page 76, Entry 605
    Source: LDS Film 1562959