Yeah, we are far from going live as it stands anyway, so we'll have plenty of time to clean up the css.
Looking at how you did it, it does become obvious I've been going about it all wrong. All styles are now properly inherited as well.
It does seem I've lost the sidemenu, but I'm still not decided on that one anyway. Perhaps rebuilding a custom one is nicer, more fitting with the theme. I'm pretty confident I'll get everything exactly the way I want it from here though!