Have confirmed that "Thomas Mathews, late Admiral, Sudbury Common ..." (1748 ref) and "Thomas Mathews, Sudbury Common ..." (1750 ref) is indeed the Thomas Mathews, Admiral, dismissed the Navy 1746. He became MP for Glamorgan 2 Jan 1745 and switched to Carmarthen 1747.
He died 2 Oct 1751 and so predates your 1764 date. More significantly, unable to pin him down to Sudbury House