Probate shows William, a manufacturer died 1820. The death record shows he was 46 so born 1774.

Name:    William Blakley
Event Type:    Baptism
Baptism Date:    23 Oct 1774
Parish:    Manchester, St Mary, St Denys and St George
Father's Name:    John Blakley
Mother's Name:    Ellener Blakley
Archive Roll:    753

There are no Lancashire deaths indexed (from Sep 1837) for a William Blackley born before 1800.  He married in 1803, so must be much older!

He most likely died in 1820, aged 46 (confirmed by Probate).

Name:    William Blackley
Age:    46
Birth Date:    abt 1774
Burial Date:    13 Jul 1820
Burial Place:    Bolton-le-Moors, St Peter, Lancashire, England
Reference Number:    GB127.L243/1/5/3

Name:    Bleakley, William
Dates:    21 Sep 1820
Place:    Great Bolton, Cheshire, England
Collection: Cheshire: - Wills and Inventories, 1811-1820 (A-L)
Volume:    List of Wills and Administrations (Infra Wills are marked with an asterisk) Now Preserved in the Probate Registry at Chester, For the Years 1811-20, both Inclusive.
Chapter:    [1700]
Text:    Bleakley, William, of Great Bolton, manufacturer. 21 Sep 1820.

Aged 68 in 1851
Aged 78 in 1861

The Nancy Bleakley that died Bolton 1844 was aged 6, and another in 1846 was aged 1

James Blakely
Event(s):
Birth: 
Christening:  06 JUN 1804   Bolton,Dean, , Lancashire, England
Parents:
  Father:  William Blakely OR Bleakley
  Mother:  Mrs Nancy Blakely 

Aged 33 when died, so born 1805, bap 1806

MARTHA BLACKLEY
Event(s):
Birth: 
Christening:  14 FEB 1806   Saint Peter, Bolton Le Moors, Lancashire.
Parents:
  Father:  WM. BLACKLEY
  Mother:  NANCY 
Abode: G.B.

There also an IGI record that indicates another Martha Blackley married Richard Kay on 25 Mar 1817

Name:    Martha
Gender:    Female
Marital status:    Married
Burial Date:    15 Sep 1838
Burial Place:    Bolton-Le-Moors, Lancaster, England
Spouse:    Richard Fielding
FHL Film Number:    1966471
Reference ID:    It 4 pg 12

FIELDING, MARTHA        33 
GRO Reference: 1838  S Quarter in BOLTON UNION
Volume 21  Page 67

Name:    Sarah & Nancy Blakeley
Baptism Date:    27 May 1808
Parish:    Bolton-le-Moors, Lancashire, England
Father's Name:    Wm Blakeley
Mother's Name:    Nancy Blakeley
Register Type:    Bishops Transcripts
Reference Number:    Drm/2/21

Sarah & Nancy, d of W'm & Nancy Blackeley of G.B.

Name:    Sarah & Nancy Blakeley
Baptism Date:    27 May 1808
Parish:    Bolton-le-Moors, Lancashire, England
Father's Name:    Wm Blakeley
Mother's Name:    Nancy Blakeley
Register Type:    Bishops Transcripts
Reference Number:    Drm/2/21

Sarah & Nancy, d of W'm & Nancy Blackeley of G.B.

ELIZA BLAKELY
Event(s):
Birth: 
Christening:  06 APR 1810   Saint Peter, Bolton Le Moors, Lancashire.
Parents:
  Father:  WM. BLAKELY
  Mother:  NANCY