Cheers Ace Dragon, had a play with this and got some interesting results. After changing things up a bit, here’s what I settled with:
Colour Ramp adjusts the “focus”, back facing subtracted out, Colour is adjusted with a colour mix multiply, strength and fall off type controlled with the Light Falloff.
Switching up the colour mix mode can have some interesting effects too.
I don’t fully comprehend all the nodes, but this certainly seems to be doing the job for me. Thanks for getting me there