After expanding a Live Paint group you will get 2 groups. One with strokes and one with fills.
If you want to keep special strokes and brushes you need to make a copy of them (and hide them) before creating the Live Paint group. After expanding the Live Paint group, you can replace the lines with the copy.
If you make a copy of everything and move it to a new layer you should be able to (with everything selected on the new layer) to just set the fill to None. Then do the same with the original artwork setting but set the stroke to None.
Thanks, I did as you said but struggled to get it to work. When I select fill: none on the new layer it just all goes white. I then did as you advised on the original but couldn't see how that would help detatch the black linework from the colour
You're not "detaching" it, your just turning all the fills to none. Every path, even unclosed ones, have both a stroke* and a fill, it's just they're either on (colored) or off (transparent). You may find that what you will acheieve when all your fills are transparent is that your strokes on sub layers are visible, and this may not be what you want...