Thanks R0J0hound - this plugin is brilliant. I've seen this asked for a lot and people have been waiting for something like this for a long time, so I'm sure you've made a lot of people happy!
https://dl.dropboxusercontent.com/u/50465867/Construct/LightCombo.capx
This is a modified version of the capx if anyone wants it. Again, you should be able to use this as an include in many other sections of your games :) Again, just make sure you have a "Light & Shadow" layer.
I've also increased the size of the pasters slightly to ensure they don't appear when scrolling to fast. This may have affected the resolution slightly, but it's not noticeable.
Additionally, the top layer can have a blur effect added to it, which will help smooth out the shadows, but this should be optional in case it slows things down too much.
Now the only issues appear to be the blend of the light sources seems to wash things out, rather than the nice blend R0J0hound is able to achieve.
Also, on occasion, the fps will dropp down about half. I can't seem to replicate this a lot, but it seems to happen when moving the lights around a lot.