Attach all objects for same material

This script is simple, we work with urban scenes, they're huge and time consuming to create.

At the end of the line we have alot of materials and it usualy takes + 3 houres to attach all objects of the same material to 1 object.

We're looking for a script that does just that with regard to

"multisub-materials" and "selected material"

Meaning objects with multi-sub-materials should be ignored and the script should only handle "single-material"-objects.

Meaning the script will lookup the objects from the selected material and only attach all objects that have that materials assigned to it (not if it's in a multi-sub-material)

This is something that could save alot of pple, alot of time...