Impossible to know until the pre-orders or regular sales start, whichever comes first. We could guess all day, but woudn't you rather waste your time ogling Page 3?
Has the NHS got discounts previously off normal Apple stock? If not, no.
It's unlikely they're going to be discounting it too much. Back to school would be more likely push for laptops. Though they could sweeten the pot and discount the iPad if you were buying both as an alternative to free/discounted iPod.