Since this thread is about WH Smith, thought I'd remind UK readers that buying from WHS via Quidco will get you a cashback of 8% of your purchase price.
If you don't use Quidco yet, then have a look at all the merchants who support it and the discounts they give :
www.quidco.com
It's quite legit and effectively the retailers give Quidco commission for passing you over, and Quidco return the money to you (less £5 per year admin, or nothing if you don't earn any commission)