Hi Muzza,
I've been playing more of this and it's great!
One issue I've found playing on MiSTer Minimig core - forgive me if this is already posted here (I searched and couldn't find it).
The scrolling on the shoot 'em up levels doesn't work, glitching to the point where it's not possible to play through.
It's documented here over on the MiSTer forum with a video example.
https://misterfpga.org/viewtopic.php?t=5910
MiSTer is usually a very solid match for the real thing with pretty extensive config options, and I'm thinking there may be a setting that fixes this.
I'll check my settings and add to this post if that's helpful.
Thanks!