Thanks for the info Jochen. I figured out the usw_load part (well, I hadn't verified since it killed the mk3, I edited all 3 using NavTweak though) but hadn't realised about the mode2 burning. I used UltraIso which changed the cdd image from mode2 to mode1.

Well, mk3 is dead at moment, but trying to revive with a mode1 disk and modified startup screen probably doesn't help

Will gice this a go tomorrow