Australian immigration records are quite variable in being able to identify people from Man. The Victorian Public Records (prov.vic.gov.au), for example, don't identify nationality online, but even from film they only gave immigrants the choice of selecting English, Scotch, Irish or Other - my ancestor chose English. In the NSW Immigrant Deposit Journals (again not online) it is relatively simple to identify Manx immigrants (code was IOM).

Search results from RecordSearch at National Archives (for post 1900 immigration) tends to provide more meaningful info about origin. And their mapping our ANZACS site allows you to search by birthplace of WW1 soldiers, including overseas locations. (Data quality isn't a strong suit unfortunately- persevere. It lists 5 from IOM UK, 43 from IOM England - and places the flag for them near Preston, 22 born in Douglas, England, 3 in Douglas IOM etc).