Harold R and Ivy V Sherriff are on the 1964 electoral roll in Lambeth at 25 Brading Road Norwood.
They are at the same address in 2002. If they had gone to Australia after 1964 there would not be a passenger list available and the births of any children after that date would not be available to search. I cannot see anything for them on Electoral Rolls in Australia or in newspapers on the Trove website.
There is an entry in the Probate Index for Harold , indicating that there is a will which may shed some light :
Harold Robert Sherriff died 31 May 2002, probate 27 August 2002. Registry Brighton. Grant and Will
number 1031934