Hey Rob,
It all really depends on what specific impression you want to do. You'd need to add small and large packs, helmet, FS or GS cap with badge (depending on impression), anti-gas equipment, bayonet, rifle, entrenching equipment, mess equipment, and other random personal stuff. WPG's package is a good start. But as with all impressions, the devil is in the details. If you want to be one of the few to do 1940 BEF, those details are particularly devilish.
Good luck!