Thanks, everyone, for your replies and suggestions. I'm sure it must be Richmond Buildings.
My 4x G-grandfather was a carpenter/joiner. Married in 1815, he and his wife had children in 1816, 1819, 1824, and 1828 (at least). Soho was at the centre of the 1831 cholera epidemic, and the 1819 child (my 3x G-grandfather) next turns up marrying in Leeds in 1839. I'm trying to work out if the whole family fled London to escape, or whether he was the only one who moved north. Problem is, the surname was Carter, so it's very difficult to track them down with confidence, but I suspect that the youngest child didn't survive, and possibly neither did the mother (cholera or childbirth?). The 1839 marriage certificate implies the father, George, was still alive, but where???