THat stout is pretty much all gone, but I did get a chance to compare it against coopers best extra stout. My stout was more bitter, and drier by a fair margain. But that was held in balance by the extra bittering. My stout didn't quite have the silky mouthfeel from the oats, as I was too stupid to add something to convert them.
When I first tasted it it wasn't sweet at all, and had a good choc/coffee flavour up front, followed by a nice roasty finish. In comparison the coopers stout was very very sweet, which is something I've never noticed before from it.
So to sum up, lactose may not be required, unless you are deliberately aiming for a sweet stout.