Please forgive my ignorance - I just don't know where to look or how to start searching English/Irish documents from Australia

I have been tracing my 5 x Grandfather Michael Dooley and historical paperwork from the Police Musuem in Victoria Australia has his application papers recording he served in the 5th Fusiliers Army for 7years. Working backwards from the papers work he would have been in the Army circa 1846.
the paperwork also says he was in Mauritius prior to coming to Hobart Town Australia around 1853. Did the Fusiliers go to Mauritius??
Michael Dooley was born 1824 in Galway ( I know this from his death certificate ).
I would be grateful for any help on how to proceed from here .
