Thank you for this, Kismet. It's really interesting and informative and I find myself tending to agree with the conclusions you've drawn from your research. I've often wanted to nail this myself, so thanks again for saving me the time and effort
Regarding the use of the term "Honourable" - in the Australian political scene (which uses the Westminster system of government) the serving Prime Minister is entitled to be referred to/introduced as the "The Right Honourable...Title...First name...Surname." But he/she would be addressed as "Mr/Mrs/Ms Joe/Jane Blow" or "Prime Minister." Former PM's are simply "former PM...name" or "name...the former PM" (if we're feeling polite...

). See the following from Wikipedia
https://en.wikipedia.org/wiki/The_Right_Honourable:
"In Australia some Premiers of the Australian colonies in the 19th century were appointed members of HM Privy Council and were thus entitled to be called The Right Honourable. After federation in 1901, the Governor-General, the Chief Justice of the High Court of Australia, the Prime Minister and some other senior ministers held the title.
In 1972 Labor Prime Minister Gough Whitlam declined appointment to the Privy Council. The practice was resumed by Malcolm Fraser in 1975, but Bob Hawke declined the appointment in 1983. The last Governor-General to be entitled to the style was Sir Ninian Stephen. The last politician to be entitled to the style was Ian Sinclair, who retired in 1998. In 2001, Sir Robert May was elevated to the UK peerage as Baron May of Oxford, which carries with it the style The Right Honourable.
Australians holding certain hereditary peerages in the grades of Baron, Viscount and Earl also use the Right Honourable title. The Lord Mayors of Sydney, Melbourne, Brisbane,[22] Perth, Adelaide and Hobart are styled the Rt Hon. The style (which has no connection with the Privy Council) attaches to the title of Lord Mayor, not to their names, and is relinquished upon leaving office."
A comprehensive guide, should anyone wish to familiarise themselves with Aussie protocol - on the off-chance that when you visit, you might get an invite to Yarralumla (Governor General's Canberra residence), The Lodge (PM's Canberra residence) or any of the Federal or State Government Houses or State Premiers for a cuppa - this nifty guide will give you all the gen you need:
https://www.premiers.qld.gov.au/publications/categories/policies-and-codes/assets/att1-forms-of-address.pdfPersonally, I'd be more over the moon to have a cuppa with Bertie and Algy than with any of the above
