As captain/master they can be tracked through the shipping reports of the period. What papers do you have access to (Trove apart)? Do you have access to The National Library of Australia - which has a range of English newspapers (Gales/The Times).
The National Archives has been mentioned and there are records on FindMyPast which reflect the NA (as mentioned pre 1835 a bit limited).
Are you familiar with Lloyds Register/Lists - again for master/captain only?.
Thank you, yes, I have been using all of these. I have exhausted Trove, I am actively using Lloyds via maritimearchives.co.uk, which is where I got the information from for the second half of my post in partnership with the newspapers on findmypast.com. I have spent hours upon hours in person looking at old documents at the NSW State Archives and the NSW State Library.
I guess I should have been more specific in my original post. I am really not expecting to find the details I need online. I want to know if anyone is aware of record collections held by an archive, library, museum etc that would have more detailed information for mariners during this period. I have not found a suitable listing on the National Archives (UK) or London Archives. E.g. I am aware that the London Archives hold papers for the East India Company (not who my guy was employed by) that are not available online so I am hoping someone knows if the equivalent exists.