As you said some years ago, both Thomas and Sarah were aged 60 in 1841, neither born in Beds. Thus their implied births were between 1775 and 1781, although their ages at burial imply births of 1771 and 1772.
As Narroway should be an easier name to research than Green, have you found where Sarah was from? Perhaps Thomas was from the same parish, possibly in Bucks.
I can't see that either of them left a will.
Did the marriage entry give a parish of residence for either, other than otp? Do the witnesses give a clue?
Have you checked parish chest entries in Leighton Buzzard to see if he had a settlement certificate?
David