Hi Emmanuel

Very helpful thread. Merci beaucoup!
I've downloaded the models in that thread and will have a play with them.

Thanks, Hans. Good suggestion.
After my initial post, I actually found a thread saying how to make glowing letters for neon signs and therein learned how to set the illum in the .mtl file to make a surface glow, so I've been playing about with a box with a glowing face.

I read up on how to install the Advanced photo renderer plugin and setting the GI to path rather than default.

I had to roll back my version 6.12 of Sweet Home 3D to 4.5 as 6.15 wasn't working properly on my Debian 8.11 machine but fortunately I was able to find a version of Advanced photo renderer that works with v4.5 and can get actual glow effects and better lighting - provided I don't have too many things in the scene.