Could this be him in 1851 Census?

William LEMON Head M 21 M Cordwainer Bridford-DEV
Eliza LEMON Wife M 20 F Dressmaker Torrington-DEV
1851 Census: Friars Terrace, Exeter Holy Trinity Exeter, Devon
http://genuki.cs.ncl.ac.uk/DEV/Bridford/

Cordwainer (shoemaker) often learnt in Prison. Guess it could be possible he came back to Devon after being transported.

Maria GEORGE Head W 43 F Manglewoman Moreton Hampstead-DEV
John GEORGE Son 13 M Errand Boy Exeter-DEV
Caroline GEORGE Daur 11 F Scholar Exeter-DEV
Charity LEMON Moth W 73 F Lodger North Tawton-DEV
1851 Census: Sidl (Sidwell) St 112, Exeter St Sidwell Exeter, Devon
Hope it helps.