Mirroring Entire Scene

I am currently in the process of wrapping up a project which features an on-rails side-scrolling scene ( left to right ) which will also be required to mirror the scene and reverse the direction.

Applying a negative x scale, reversing mesh triangles and fixing up the normals appears to work okay for the geometry, but wrecks the lighting.

I've tried inverting the w component of the tangents to see if this would solve the issue which I presume to be relating to normal maps, but this doesn't seem to be enough as the lighting is still 'wrong'.

I was wondering if anyone else here has had to solve a similar problem and if so, how you went about effecting a solution.

Many thanks in advance.

Rob.