How to mirror an object made of several meshes?

I have this building that i would like to have mirrored.

It is made up of of several meshes that i put in a blueprint.

I need it several times and half of those times I need it mirrored.

Scaling the entire object doesn’t work as all the meshes are scaled in their local axis for some reason.

[This is described here:][2]

Is there any way to mirror the entire structure without making a second blueprint and mirroring every mesh by hand?