Right, I've found out how to do it and got the hand of it (keyframing). However I have one problem.

I'm finding it really hard to keep it smooth. The blue screen layer, is really hard to keep in the exact same spot every frame, I am doing this every single frame for the whole clip and it is really time consuming, the result of a smooth "looks real" feel is seeming impossible to achieve. Any tips or tricks at all on doing this?