Not sure what you mean by Mary Ann 1805 born London?
1851 Census Mary A Pearson is born c 1804 St Gilles, Northamptonshire (as transcibed Anc)
1861 she is under Mary A Weasson c 1802 Northamptonshire
1851 they have a Daug Jane;
PEARSON, JANE mothers mn PEARSON***
GRO Reference: 1845 J Quarter in HARDINGSTONE UNION Volume 15 Page 267
Trish

EDIT
GEORGE Pearson bapt 21 Mar. 1802 St Mary the Blessed Virgin, Great Houghton to PETER/MARY
Birth 4 Feb. 1802
Siblings;
Michel 1785
Isbell 1787
Tabbatha 1789
Ann 1793
James 1796
Peter 1799
OOH my gosh;
Marriage;
06 Feb 1785, St John the Baptist, Piddington
Peter PEARSON to Mary PEARSON
All on FreeREG