The Battle Spec stormtrooper helmet by Shepperton Design Studios is a rather nice helmet - it should be because Shepperton are the original makers. BUT! (but?) if you want to go trooping with it then the helmet needs a few modifications...
If you haven't done so already, take a look at what the helmet looked like out of the box to see why some of these mods are needed.
First off, the helmet needs to be taken apart and can be done easily by removing 6 screws. The sponge is loose and the brow comes off easily too. The green lens that comes with the helmet should be set on fire and the ashes should be flushed down the toilet together with your morning dump.