I always get the power formula mixed up when it has resistance in it, my bad.
I did want a continuously variable output so I think Roff's circuit could work well. It shows the LM350 but from the datasheet I think the LM317 would work just as well.
Shame that it needs an op-amp but oh well, would a 741 be fine ? I have no other use for the 741's that I have lying around here ..
How big would the heatsink need to be for a LM317 with in input voltage of 12V and an output voltage of 8V @ 1.5A ? Would those tiny clip on heatsinks work ?
Thanks for all of your help guys.