Martin,
I only have Thomas (b. 1760) as son of Joel Singleton. But Thomas' sons were Thomas, Samuel, Joel, Francis, Benjamin and William which matches the ones you mention from Nottingham. Could be a possibility.
As for Chillington records. There are Bishop's Transcripts from earlier years at the London Family History Center (Mormon Church)
Note Location Film
Baptisms, marriages and burials, 1599-1641 (some years in Latin), 1678, 1689, 1707, 1785, 1790, 1801-1833. (Not complete for all years and some years in poor condition.) FHL BRITISH Film 1278918 Items 9 - 10
Other than that I don't think the Somerset HC has previous records (that I know of).
Regards,
Carlos.