Hi, I see you are posting on the Merrett family of Clapham. Some Clapham baptisms are not on the IGI (despite the fact they say they are) and the Merrett family are among them. I am descended from Henry MERRETT and Amy TAPLEY married in 1848 in Clapham. He is the son of Charles MERRETT who was born in Clapham in ~1807 but lived in Stockwell. I cannot find Henry's baptism but he is on the census.
Here are some MERRETT entries up to 1813 from Holy Trinity Clapham:
c. 14 Feb 1803 Sarah MATTHEWS 1st daughter of Richard (labourer) and Ann MERRETT [sic] (b. 26 Jan 1803) (4548)
c. 10 Aug 1803 Mary MERRETT 1st daughter of Thomas and Mary HILLIER (b. 27 Jul 1803) (4611)
c. 20 Jan 1805 William MERRETT 1st son of William (gardener) and Elizabeth (CARTER) (b. 12 Jan 1805) (4826)
c. 17 Mar 1805 Ann MERRETT 2nd daughter of Richard (gardener) and Ann MATTHEWS (b. 24 Feb 1805) (4835)
More Sierra Leonean baptisms on 12 May 1805
c. 6 Jul 1806 Susannah MERYETT [sic] 2nd daughter of John (smith) and Elizabeth MOULDESWORTH (b. 12 Jun 1806) (5051)
c. 12 Dec 1806 Richard MERRETT 1st son of Richard MERRETT and Ann MATTHEWS (b. 19 Nov 1806) (5117)
c. 24 Apr 1807 Abraham Carter MERRETT 2nd son of William labourer and Elizabeth CARTER (b. 3 Apr 1807) (5171)
c. 5 Oct1808 Jane MERRETT 3rd daughter of Richard MERRETT and Ann MATTHEWS (b. 15 Sep 1808) (5422)
c. 15 Jan 1809 Eliza MERYETT [sic] 3rd daughter of John (smith) and Elizabeth MOULDSWORTH (b. 16 Dec 1808) (5473)
c. 13 May 1810 James MERRETT 2nd son of Richard (labourer) and Ann MATTHEWS (b. 23 Apr 1810) (5712)
c. 18 Jun 1811 John MERYETT [sic] son of John (smith) and Elizabeth MOULDESWORTH (b. 24 May 1811) (5913)
c. 2 Feb 1812 Mary MERRETT 4th daughter of Richard (labourer) and Ann MATTHEWS (b. 13 Jan 1812) (6031)
c. 26 Jul 1812 Caroline MERRETT 1st daughter of William MERRETT (gardener) and Elizabeth CARTER (b. 3 Jul 1812) (6126)
Adrian