Final Composite

This is the final composite. I have added some color correction to the foreground footage, reduced the saturation a little. Around the edges of the foreground I've blended in some of the background color, to reduce the 'cut-out' look. This was done using a 3rd party plug-in. I've also added a little bit of glow around the highlights.

To finish the thing, I've added a little grain to the overall image, to match the computer generated background with the foreground footage. If the foreground footage is very grainy, you could choose to add grain only to the background, to make it less artificially smooth.