Only West Marylebone baptisms 1842 +- 5 yrs I can find on ancestry, both Christchurch, are Sarah West d/o John, gardener, & Sarah 18 Salisbury St on 1 Jun 1842, same couple had Richard baptised 12 Jan 1845 now living 3 Hardington Place.
ADDED:
Also 11 Nov 1849 John & Elizabeth baptised of John, gardener, & Sarah 16 Weston Place
This I think is Fanny [10 in 1851 in Burns Place] but cannot find a baptism
Births Sep 1841
West Fanny Marylebone 1 175