Order a Free Pay As You Go Sim from Vodafone with a £10 topup and they are giving back a Free NUS Extra membership for Students.
That represents a £2 saving over just buying you NUS Extra membership direct from the NUS.
Good deal to save a couple of quid and get a months usage of the network too.
Do consider this bit - To be eligible for a NUS extra card you need to be over 16 years old and in full or part time education
Quidco / TCB offer a cashback of £6