...and since this thread seems to be chirping with various flag bits not necessarily related to the OP, in OZ there's also some confusion between the Australian Red Ensign (the UK Red Ensign, but with the Southern Cross stars in white against the red field) and the National Flag (the same flag, but with a blue field) with the Red Ensign now officially only for vessels on the Australian Register of Ships.
So any Australian-registered non-military vessel overseas should fly the Australian Red Ensign. Vessels visiting Australia
, however, should fly the National Flag as their courtesy flag.
Back to our OP and to further assist his/her immediate flag selections (and ensure a warm welcome throughout the UK!) we suggest the 'Splice The Mainbrace' flags
. Steeped in British Naval tradition and with a very fun modern usage (basically Cocktail Hour for all!) the four flags
signalling Splice The Mainbrace will be welcomed anywhere mariners know thier flags. A short version of the history
Splice The Mainbrace Flags, Floating Impressions
Fair winds & following seas to all