Thought the Space bar might have been wrong in the instructions, thinking about it, I remember having to waggle back in the day
I didn't know of any Wizball corruption, I've made it from the only version that I could find without trainers or intros that needed keyboard to get past as I don't know enough to remove them, I used the CRACKPONX version from CPCRULEZ &#9733 AMSTRAD CPC &#9733 GAMESLIST &#9733 WIZBALL (c) OCEAN
CPCRULEZ ★ AMSTRAD CPC ★ GAMESLIST ★ WIZBALL (c) OCEAN
There is a stack overflow at some point in the game, near the end that make the background (of level 6 if i remember well) all corrupted, and sadly Wizball interract with the background. Hence, it's really difficult to finish the game, as you have to go to level 6 only when you are 100% sure that you will go to hyperspace at the exact moment you enter it.
With save states, its finishable, but without it, only one mistake, and your screwed.
The fix is here :
http://www.cpc-power.com/index.php?page=detail&num=1670at the end of the page, i don't know if it would work with the version you took.
The latest version from CNGSOFT looks nice, it has a new loading screen but it has a trainer at the start which needs the keyboard, maybe this can be removed or bypassed, no idea if this version has the corruption you mentioned.
CNG Version has the fix : "stack overflow fix by Crackers Velus and Kukulcan". But yes, it has to be fixed for the trainer