OK, folks. This isn’t quite in the final state, and there are a couple more things I want to add, but it works with just a little user tweaking now, and so I figured ready for a release. This uses a modified version of a node setup I found to work very well for both shadows and reflections. The plugin will set up your scenes, layers and the compositing node setup. There are just a couple of preparation steps that you need to make it work, which I’ve covered in a brief video at https://www.youtube.com/watch?v=M2LgAytYRts&feature=youtu.be
EDIT: I should add that, unlike some other methods, this works with lights, emitters, HDRI, AO, caustics and reflections. You can effectively do a complete composite.
Give me a shout with any problems. Hope you find it useful.