Hi,
For best performance you should use
* DC instead of PWM (not pulsed, not ON/OFF)
* a switched mode controller instead of linear current regulator
* current control instead of voltage control
Did you do a search for suitable circuits?
About the temperature regulator:
There are many options, depending on your requirements.
* absolute temperature control / difference (relative) temperature control --> 1 or 2 temperature sensors
* what human interface? Pot, Led, PC, display, keys...
* regulation speed, accuracy
* what are you trying regulate? And by what values (error) is it influenced! (Ambient temperature, load temperature, Q...)
Klaus