UE5 Strange Lighting problem in static mesh (tangents?)

Hi - My meshes are behaving strangely when imported in. The shading seems very dark on only some faces. Have checked all the normals etc before exporting from Blender. When rotating an object the light seems to move in different directions on faces that are facing the same direction.

I checked various things, normals etc and on the tangents in the editor - some of these seem to be pointing the wrong way which I assume is the problem - how do I fix this?

In Game

In Editor (missing the top section which is a separate mesh)

Do you have a skylight?

I have a directional light?

You need a skylight as well…

Looks like your vertex normals are all screwed up, no idea why