Windows 8 only includes AppLocker support in the Enterprise version (Where as Ultimate and Enterprise had it in Win7) it's there in Win8 Pro but doesn't enforce the rules.
SRP runs in usermode and doesn't allow exceptions so it's off the cards.
And volume licensing is 5+ from what I can see...
Is there a way I can get Applocker without having to spend a huge amount? I only need one license.