Just as a note which may be of interest to Andrew, I found William Clay Carter, a builders foreman, et al in Islington on the 1881 census and then a death for him in Islington in the March Q 1888 age 61. Don't know what time frame you are looking at in Islington Andrew but thought I would post just in case.
The death for Thomas Clay in 1846 is not he. This was St Albans RD but was at Harpenden and not the right family. There is another though in 1850.
To JLo, watching this space, thanks for your message.
Cheers
Denise