Sue: I never did order the cert copy from FreeBMD, but have done so today (for Sophia Jane). Thank you for prompting me to do so Sue, I don't know why I never thought to do so previously...
I don't have an Ancestry.com subscription and only have access to the site when my husband's cousin is away and she allows me to use it. So, I have not yet seen the 1841 census you refer to, however, and unless I'm reading you wrong, it would appear that the name of David's spouse is Sophia, aged 20 years, which is incorrect; I'm looking for spouse Eliza/Elizabeth. The 1 month old Sophia of course could have been the daughter Sophia Jane.
Thanks again Sue.