Well, here goes with my update, and I can report it is good news!

First, a confession (or two); I don't think the CyberStorm 060 was actually at fault, ahem, I didn't see the rainbow on the screen because the bloody SCART cable wasn't in the back of the TV correctly! Major embarrassment!
Anyway, after fathoming that out, I still had my red screen appearing on the ESM.
So after removing and cleaning and drying out the Zorro cards, daughterboard, ROMs, Buster, CPU (even though it was working at this point, can't harm it) and anything else removable, with IPA, I slowly started putting things back into place; one at a time.
Buster, original 3.0 ROMs and CPU went in first, followed by 32Mb at a time right up until I had a full 128Mb RAM and a 060 working nicely.
Scandoubler, no problems there.
Next, the daughterboard, still no problems.
Ariadne II in next, yey, still no problems.
CyberVision64... BINGO. Red screen of death. Seems I confused the CV64 and CSMkII because I only checked the Manufacturer ID, but not with the Product ID. Double-d'oh!
Luckily, and I have no idea why I do, I have 2 spare daughterboards with my A4000, two from '92 and one from '93. I currently had the '93 one in. Why not, I'll swap them out so I put the other '92 one in, same problem, so I didn't hold out much hope for the third and was ready to concede that the CV64 was bust. But no, the third daughterboard gave me back my CV64, and Ariadne II so all is, hopefully, now well!
Short version: CyberStorm was fine, SCART cable was half hanging out, daughterboard was defective, new daughterboard in and everything is fixed!
Thanks to you all for the suggestions, and offers of help with this. I now have my lovely A4000 back and sitting next to my A600 and A1!