Really? When I last went to the National Archives, because their own building is being re-furnished, on a long-term basis, The Latter Day Saints Family Search have their own area where they have all of the microfilms/fiches and computers. I have obtained many documents from this, however I would recommend to you, the descendant of Ernle, getting the marriage certificate, searching for other Drakes born around that time in Bath- who could be relatives or siblings, trying to search for a marriage of his father, looking at newspaper articles, and finding him on the 1841 census, as you didn't say you had found him.