Hi Neil thank you for taking the time to look, in answer to your question as to whether they definitely headed for Brisbane I found the following on "Find my Past" on the Passenger List leaving the UK 1890 to 1960:
SIMCOCK Simron
D.O.B. 1875
MALE
DATE OF DEPARTURE 1900
FROM LONDON
TO BRISBANE, AUSTRALIA
SIMCOCK Maggie
D.O.B 1877
FEMALE
DATE OF DEPARTURE 1900
FROM LONDON
TO BRISBANE, AUSTRALIA.
There is a spelling mistake in that Simeon's name has been spelt Simron, and they both seem to have gained an extra year on the birth dates I found on Staffordshire BMD. I searched on Staffordshire BMD's and found Simeon and Maggie's births, Simeon's christening record and the marriage record but no death records for either of them, it was a relative who mentioned that my great grandfather's brother had emigrated and initially I thought it might have been New Zealand but after doing some digging around I decided to try Australia and it was suggested that "Find my Past" may help, I did and the above is what I found. I did wonder if I could try shipping lists
