Lighting failing at render stage

I've been playing with some basic particle stuff and got a scene I liked in my 3d Merge window which is then completely different in the final render. I've enabled lighting on the render node but it just doesn't seem to be working. There are no nodes between the merge 3d and the render 3d so I'm not sure what could be happening. If anyone can shed any light I'd very much appreciate it. I've attached a screenshot for reference:

fusion particles.PNG (161.46 KiB) Viewed 686 times

Add a background / disable the checkerboard button