Thankyou all for your posts and suggestions....do have an excuse for not posting as regular of late - summer heat in Australia unfortunately brings bush fires and some have been too close indeed....priorities are put into perspective on such occasions.....

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Anyway here's a rather long winded reply to some questions - firstly I must thank others for running with this - it is truly inspiring and I have nothing other than admiration for you work....well done!
My belief of he being born in Northumberland primarily stems from earlier research coupled with comments from his descendants (when I started researching for them) who believed so from what they had been told by their grand parents etc...but then they were not aware of Blakey!
I have also seen photographs (poor quality and quite flimsy) believed to have been of Joseph that were endorsed with faded hand writing on the back stating "Joseph M North'lnd" - it was not known who wrote it nor what it signified - unfortunately I did not take copies when shown some years ago.....I have since been informed the person who had them is deceased so I cannot access them again
When I had the chance I have been chasing up the children born in Australia from the marriage of LOWE and MASON...in the hope they may shed some more light ....early documentation in Victoria often shows the place of birth of the person..such as Victorian marriage, births and death registrations...sometime there is a Will which can be access as with probate....so its these I have been chasing up...
Along with his arrival in Australia, I am still yet to find any proof positive deaths for either Joseph or Elizabeth - but here's what I have so far....
Mary Mason, was born on the 18th June 1867 at Majorca in Vic....(Joseph and Elizabeth were married on 24 July 1867)....in the 'father' column I cannot decipher the word written in it (possible "not stated") but definitely not a name and definitely not Joseph Mason yet he was in attendance at her birth because he signed his name as the informant, a father and residing in Majorca (in Victoria) ...... in that order.....whether he was 'her father' not stated and he definitely did not complete the father column....Elizabeth stated she was the mother and born in Kings Country Ireland, was 33 years old.......
Interestingly if he was her father then he would have had to state his country of birth and age in the father column...that was a legal requirement on Birth Registrations then.....he did not....another omission perhaps???
Mary died in December 1948, her son who completed the Death Registration stated Joseph Mason was her father (unfortunate he did not state where he was from) and he did not know who her mother was (which would make her his grand mother) so he wrote 'unknown'...indicating Elizabeth may have died (moved on?) before the informant knew of her but equally his mother never told him of his grand mother, but he did know his grand father was Joseph as filled that in.....strange?
Mary spent a great part of her life residing in Ararat
The other child Adelaide Ann Mason was born in 1870 (yet to obtain her certificate) - died in Sep 1955 in Ararat and spent most of her life there...on her registrations (birth and death) both her parents were listed as Joseph Mason and Elizabeth Lowe - unfortunately no other details listed for them......so her descendants knew of Joseph and Elizabeth
The common factor that I had to work from this family as told to me was a connection to the town of Ararat in Victoria...most of them lived and died there allegedly including Joseph and Elizabeth.
The only Joseph Mason who died and had a connection to Ararat (through Probate records I accessed did not list his POB only POD and occupation) died in 1887 at a hotel in Melbourne - Probate listed him as a Gatekeeper at Ararat - there was the only connection) .... I have not been able to access his Will as only available in Melbourne with physical lookup, not online.
This is where it gets ever stranger.....his Death registration was filled in by the owner of the hotel, chap named Heffernan, the Publican and also the Informant: according to he, this Joseph Mason did not have any family, was born in the USA and stated Joseph had lived in Victoria for 20 years.....that would have made his arrival about 1867.
I could not find any family death notices, funeral arrangements or other aside from a notice in a regional newspaper as to the Death of Joseph Mason at a Hotel aged 55, no family was mentioned...this Joseph was subsequently buried in Melbourne New Cemetery not Ararat..(Ararat and Melbourne are approximately 200 kms from each other) - his family lived in Ararat, he worked there so why was he buried in Melbourne??
Sorry to be so long winded....will keep looking over here and see if we can find out what happened to him and his wife Elizabeth....