So Long Seams
After some research and being pointed to a great forum post on the Epic forums I have pretty much solved my issues with a few bits here and there that can be covered.
It required adding an additional lightmap UV channel in 3DS Max, which then is specified inside Unreal.
After doing this for each modular piece, I then had to change the world lightmass settings to give a betrter quality of lighting. This all only looks acceptable with a production level light build.
So I’m back on track and churning out 3D models quite quickly now, the scene is becoming filled.