Update 1:
After about 4 hours of work, I've finally gotten the Hexagonal Grid to mostly work! Currently, it simply allows the selection of the starting cell via its coordinates set in the game manager, and then makes its neighbours visible thanks to some (messy) lines of code to calculate which cells they are. I had a fair bit of trouble getting the neighbour system to work, but with a method to make them visible and a few bools to let the game know that they are visible, I think it's finally stable! ^-^
The green cell is the starting cell, the outlined cells being its neighbours
There's an underlying 21x21 grid of hexagonal cells that aren't visible, so that instantiation of the cells isn't required during playtime, and since the play-space will be limited.
I also quickly put in the place the simplest of UIs as can be seen.