Your current is up to 1,2A so any transistor that can handle the double to be safe, could be used. TIP31 (3A) or MJE3055 (10A) are a few examples.

The idea is to design a simple classic linear power supply that would be controlled by your PIC about the voltage and current. That would require A/D converters but to be very fast, a good designed Sigma-Delta converter may have to be used instead off the classic ADC's.

That's what is hidden in the Elektor's article I mentioned.

Ioannis