Many thanks Ronjonp.
I downloaded the 2013 version from the list you provided and after a run-around where I was told that my Microsoft.NET Framework needed to be updated, which required 2 different approaches, found by a Google search, and then re-booting more than once, it actually worked and I nearly fainted.
I have made sure that I keep all the necessary files and I will write myself a proper installation note for if it happens again.
I have always debated with myself as to which company was the most frustrating, between Microsoft and Autodesk, and I have decided that it is a draw.