according to that website that SS linked too - for Australian and Zimbabwean licence holders
"# you can drive in Great Britain (GB) on your full, valid driving licence from Gibraltar, Guernsey, Jersey, Isle of Man or a Designated Country for up to 12 months from the day you become resident in GB
you can exchange your licence for a British one within five years of becoming resident
if you haven't exchanged your licence for a British one before the end of the first 12 months of becoming resident, you will need to stop driving"