So it was that I decided to go right back to the basic facts and proof that I had: the birth certificate for Constance Mary Ashton (Mark's mum), which shows her dad John William Ashton and mum Gertrude Constance Musk. I was also lucky enough to have found a copy of their marriage certificate amongst some paperwork that we inherited from Mary. I used the latter vital record to apply for each of their birth certificates from the General Register Office in the UK, and once I have those I will keep working back, ordering more and more vital records as information presents itself and I can build a good fact-based argument for each step back in the history of this family.
In the meantime I also decided to adopt the Research Worksheet I had learned about while listening to episode 23 of Lisa Louise Cook's Family History Podcast. With a background in journalism, and a pedantic streak a mile wide, I love recording information in the clearest, most concise way possible, and the Research Worksheet provided by Lisa, which makes use of the Genealogy Proof Standard, is fantastic. I simply tailored it to fit my own needs (and see myself tailoring it to fit each research goal) and used to create a solid foundation for the argument that the John William Ashton listed on the birth certificate of Constance Mary Ashton, dated 17 May 1926, and on the marriage certificate of Constance Mary Ashton and Peter Eden, dated 12 April 1955, is the same John William Ashton listed as the son of Thomas William Ashton and Rachel Mary Ashton (nee???) in the 1911 Census of England and Wales.
As is evident I decided to go right back to basics and to even use the Research Worksheet to provide an argument for something I was already fairly certain about... my theory was that, in this way, any future Research Worksheets would build upon the surety established in previous ones.
I am also trying to figure out how to work out death dates and order death certificates from the GRO, but have so far not found much information about this.