Boffin1:
Basically if you are driving LEDs with a constant current source, you do not have to concern yourself with what voltage is being applied to the LED ( or series chain of LEDS ) the constant current diver will take care of that and supply enough voltage to ensure 20mA or 1 amp ( or whatever you have chosen ) through its output pin.
Thanks Boffin1... I had a feeling I was missing something plainly obvious.
And indeed I was. XD