The timer relay along with the NTC sounds interesting. I will research timer relays to try and find what I need but aren't they a fairly standard component for this purpose? i.e. taking over from the thermistor once it has done its job so that the thermistor isn't always on and running hot. I'm guessing that the relay kicks in when the thermistor resistance drops as it gets hot (and current increases to trigger it) then it runs in parallel with the thermistor but breaks the thermistor circuit? Ive just about finished the mechanical side to my build and now im trying to get my head around the electrical / electronics side of things.
Kind regards ...Chris