Everything is back together, deja vu... I swear I've typed that before. But more problems, er problem. The new thermistor is working, the temperature is showing about 4 degrees higher than the old one. The problem is the heater is not working, it came on briefly when I first connected it went to 45C and back down, but a shutdown and computer reboot later it's not. The PWM light is coming on for the heater and it's clearly not an issue with the Reprap host software, so assume it's a short in between the PWM driver board and the nichrome wire.
I'll have to fix that in the morning. Time for some beer.