That's actually exactly what I bought at Reaper. The soft plastic models are a bit soft and rubbery, but ok overall. The bigger problem is the size. I bought all three types and none of them really fit:
Big Spider: Way too big for Shelob or any kind of Warmaster base. It's maybe 6cm by 6cm. With some bending of legs it might fit onto a 40mmx60mm base like a Stegadon but even that's pushing it. I don't think I will use this one, or maybe turn it into a Giant Spider with howdah for the Goblins (matching the new Warhammer model).
Medium Spiders: These are about the right size for Shelob, but just too big to fit onto a 20x40mm Warmaster base (too wide). I bought six, hoping to make them units, but I guess I will just use one of them as Shelob.
Spider Swarms: These are too small to match the GW models individually but too big to fit onto a Warmaster base as a group model (the model is a rough 30mm circle).
So I am tempted to use just one medium spider as Shelob on a character base, and buy some other models for the spider unit. Any ideas?