It turns out I was making a very rookie mistake. After sculpting my model (and its parts) and retopologising them, I was merely “hiding” the sculpts in a layer.
Yea… that will do it for the file size… duh!
Back to my previous workflow… 🙂
Base Mesh, sculpt details, retopo, delete sculpt, set UV, paint and texture, rigg and animate.
Ok, back on track!