I've got it to work through using the Alternate Download Mode. For anyone else reading this, you can enable this in the 'downloads not starting?' menu.
My only assumption, and this is coming from a CS student with no knowledge of how Itch's server clusters are set up, is that using a device with a UK based IP address is having me pull the file from an European server that's on the blink that other users are avoiding by simply being directed to alternate instances of the file in different locations, could be worth trying with a VPN to verify, but it's the only reason that comes to mind for this consistent failure and it's resolution through Alternate Download Mode.
Thanks for the responses though, I know it can be a headache and a half when Itch decides to be, well, Itch, and the game so far is proving worth the effort, even if I must admit there were points I was tempted just to walk away and hope Itch pull themselves together in a week or so.