And then wrote about it a bit. But I'm pretty pleased with the whole set up, in that it actually cuts!! After that it's just like using it like a pen, write the SVG or GCODE and good to go.
There's a couple of extra steps, I have to get it to "draw" the same path a few times, getting deeper each time so it can cut through various thicknesses of paper/card. And I have to leave little "bridges" or gaps in the cut so the whole shape isn't truly cut out, you have to go and snap off those little bits. Fairly standard but it makes all the difference to getting better simple shapes cut out.
I still need to wrap that logic up into code, where to place the "bridges", but that's a problem for another time.