SIS PSP22 is just an energy drink, no electrolytes as far as I can see: www.scienceinsport.com
Go is their electrolyte replacement drink btw. Or the unflavoured Torq Energy, the natural one from torqfitness.com. All the electrolyte replacement versions are going to have electrolytes including salt, so you want a pure energy drink. I'm sure there are others out there as well.
They have salt in for a reason Luke. IMO it would be better to cut salt down elsewhere. Anyway if you're exercising then you require more salt than someone who isn't, so you can probably get away with it. Are you acting on medical advice from someone who is aware that you're more active than the average person?
Luke, salt as in the stuff you sprinkle on yer chips is very different from the "salts" i.e. electrolytes found in energy drinks etc.
To be honest if you've a healthy diet and don't add salt to your food then the energy drinks aren't going to have much of an effect on your sodium levels as they're designed to simply replace what you lose through exercise.