So as soon as Ben put up the pseudo code for the lecture, I paused and went at it. I didn’t get it right off, but after I looked through my notes and thought about it for a bit I got there. I even divided by 10 for the grid and after doing so realised I should have used gridSize 
A mistake I made was recalculating the coordinates of the cube again because I put it in a separate method. Whereas if I’d kept it in Update() I could have reused the snapPos variable.
Pleased I’m finally getting it now, still not 100% on when I need to create a variable to access the data, but I guess if I think about each component as it’s own class I should get there most of the time.