Wow, thank you for all this information. I had a look for Caleb snr last night, and came up with what I think is him and his family in Dowland, Devon. He's been mis-transcribed on Ancestry as Caleb Hall, he was born in 1807 and is living with wife Mary, and children William 9, Caleb 8, and Jane 4 months and is a smith. If you look at the image, the surname is Heale and not Hall, in my opinion, anyway. It's Registration District Torrington, piece 251, book 3, folio 6, page 7, if that helps to find it. I'd welcome the opinion of anyone here about whether it is the ones I'm looking for. From the other censuses of Jane in later life as Jane Humphreys, the year of birth does fit. I'd misread her age on one of the censuses and thought she was born in 1846, but it turns out it was 1840 or 1841.
I'm in a bit of a rush at the moment. I'll come back later. Thanks again.