Have done some bug hunting and added a few more things. Most notably, now you can shoot the Invaders bullets (or to be more precise - they shoot yours) except for the 'plunger' that destroys your shot but carries on.
Damien's moon is back to orange too!
Readme file now present on the disk with lots of thank yous (have to load WB first to see readme).
Hopefully all good to go?
I have one more possible overlay to do and then I'll stop and upload it to my website!
https://eab.abime.net/zone/Space%20Invaders.adf