Student membership is available very cheaply, and membership gives you discounts on various things, as well as a magazine, access to their on-line library and various other benefits.
(Updated by NP) You will need to get one of your tutors to sponsor you. Fee is currently £17 with discount for multiple years (max of 4years), so worthwhile to join up for last portion of your degree. They accept credit cards and cheques — I am awaiting response for alternative payment methods (eg Paypal, direct debit, etc), as I have neither. :-)