Ok, getting somewhere now...
Had a thought earlier of adding a few extra loops to knock down the '32bit only' divide into sections dealing with only 32, 24, 16 and 8 bit divides.
It's working well in the short tests, sometimes knocking cycle counts down by more than 3/4, usually by about 1/2.
Fairly sure I fixed the 0/0 bug also...that could've been a bit more obvious...but I don't see how.