rob: these smaller particles may have different rules to the ones they create.

Alright you've lost me there.

rob: Every single particle is made up of smaller particles;

Superstring theory states that the smallest piece of matter/energy is a string; open or closed. The unique vibrations and 'spins' of these strings determine its properties.

In quantum mechanics, there is much that happens without determinism, and therefore we could not possible simulate a world on that scale.