It is related. I've actually fixed all the problems I had by referring back to the spreadsheet and sort of ignoring the UserForm, so...
Instead of the "set all" button changing the value of the individual control buttons, it directly sets the controlsource cells on the sheet: this fixed the problem of my code "skipping" some buttons
Instead of using a Userform change event, I'm running the code on the worksheet calculate event. Yes it's not very subtle, but it works every time.
Well...I say that it works every time...the issue I've got at the moment is that my version runs fine until I make any changes and save it - then when reload it and click the button that opens my userform - it crashes Excel. If I delete my button and recreate it, it works again.
It's probably some setup command that I am unaware of and thus have missed out causing the instability. Trouble is, I don't know how to bugcheck for that.
Oh and thanks for the link!