Sorry I’ve taken so long to get back to you.
Firstly – Samuel Underwood. Unfortunately Bedford library did not have the baptism circuit book after all so I couldn’t check it out for you. Perhaps someone else could check at Luton library for you?
I then checked a few of the other 1851 census index books & also came up blank! (Can’t find my piece of paper though with the volumes I checked – sorry

)
Checked Clophill PR Marriages 1807 Au 18 Thomas Underwood = Elizabeth Smith (no other info I’m afraid)
Checked the burials at Clophill on the fiche – some of which were unreadable because they were so faint.
1813-1850
No 705 Isaac Underwood Clophill Feb 25 1847 aged 23
killed by accident (written underneath)
No 724 Thomas Underwood Oct 5 1847 aged 65
IGI Have you seen these? All at Harper St Wesleyan Methodist, Bedford
Isaac Underwood bn 12.1.1824 c 8.2.1824 son of Thomas & Elizabeth Underwood
George c 23.1.1832 son of George & Mary Underwood
Ann bn 25.8.1823 c 3.2.1834 dau of George & Mary Underwood
Possibly a newspaper article/obituary for Isaac somewhere perhaps?
Think all the Methodist baptisms tie in nicely, with Samuel, George & Charles all in the Methodist or Weslyan Bedford Circuit book. Elizabeth & Benjamin bp at Clophill Parish church for some reason though.
Thomas Underwood is also mentioned in the will of Richard Brooks of Clophill 1810. (May be other refs)
http://blars.adlibsoft.comIf there is anything else in the registers you would like me to check just ask.
Regards
criggy