I did a fair bit of work on the BROWNs of Dunton some years ago. My notes have got all sorts of bits added, so I must have extracted them from the Parish Register, but, to be honest, I no longer remember having done it!
Anyway, I have the marriage in my notes, so I'm pretty certain that the user sub is completely accurate.
There seem to be two relevant Thomas Browns.
Thomas, bapt 30 Mar 1757, to Henry and Sarah
Thomas, bapt 16 Jun 1759 to William and Lucy (nee Peck)
I have a burial for Henry Brown, farmer, 21 Oct 1784, and ...
I have a burial for William Brown, farmer, 15 Mar 1777, and ...
I have recorded that both these gentlemen left wills. So, if somebody wants to look at the wills on a visit to the Record Office, that may clarify some things. It looks as if William died too early to be much use, though.
There are two marriages,
Thomas Brown to Elizabeth Leonard, and ...
Thomas Brown to Mary SAUNDERSON at Biggleswade (not Dunton), 27 Nov 1778 (two of my Saunderson family married Dunton Browns, which is why I did this work).
Henry and Sarah Brown seems to have had a short stay in Dunton, over about three years. It's quite possible that they weren't resident, but were baptising in Henry's home village. Given this, I think it quite plausible that the OP (whose posts elsewhere I have read!) does have it correct, assuming of course, that he can corroborate the Roxton connection.