I finally got round to replacing the laser with a KSS-210B. I purchased the laser from a UK seller on eBay for £9.99 including postage and followed the guide located here
. It was much easier than I thought it would be, only took about half an hour.
It now reads CD-Rs with no issues. The discs I burnt before that didn't work now work fine and even the discs that did work load much faster now. Original CD32 discs still work as well of course.
Amazingly I got this result with no adjustments to the pots on the laser or the controller board, I guess I was just lucky!
Highly recommended upgrade