Spot on chaps. 
thank you kindly.
And its funny you should mention that goforsmoke, as that's how i have it setup, and hadnt noticed initially (and was wondering why it wasnt working)
got my code working well, now just need to adjust my sensor.
Ive done it with no lightsource, and i think it is struggling. I think i need to work out how to add some LEDs to the current setup without too much modification...