Rory - very nice. It looks like a great game. However when I first saw it, my first thought was that it wasn't pixel art (obviously, it is!) But it's quite high resolution pixel art. I think the effect would be much more noticable if you were do a game that was in a 320 x 180 resolution.
Just as a test, I'm learning the basics of GML in gamemaker studio 2 to recreate the exact thing I'm doing in c3 to see if I get hit with the same problems.