I suspect the problem was overheating more than wearing out the flash, but dunno.. totally dead now.
Or perhaps not.
I've dug out my old notes from back when this SSD was state of the art. After attaching a jumper to the "factory" pins, it came up in "factory mode". A bit of searching around, and I found the latest v1.7 "destructive firmware update" for the unit, which works in "factory mode".
Update applied, drive is now alive again.
It was running v1.6 before the crash, now has v1.7 on it.
Dunno what the differences are.
I don't expect a huge amount of life is left in the drive, but it's probably still got 20-30% in it yet.
Cheers