Australia has 3 time zones:

• Eastern Standard Time, which is GMT +10 hours, used in NSW, VIC, QLD, TAS, and ACT
• Central Standard Time, which is GMT +9.5 hours, used in SA and NT
• Western Standard Time, which is GMT +8 hours, used in WA

All States and Territories save for QLD, NT, and WA operate Daylight Saving Time generally from October through to March, which increases the time difference between the UK and Australia.

For reference, Sydney is in NSW, Adelaide is in SA and Perth is in WA. London operates GMT from late October through to late March, when British Summer Time is adopted.

In general, during the UK summer the time difference between London and Sydney is 9 hours, whilst in the UK winter the difference is 11 hours.