I am afraid this is exactly why WH Smith is not somewhere I ever go unless I can help it. Every time you go in they have these stupid offers designed just to waste stuff as the OP found - has anyone asked WH Smith how this plays in to their "sustainability policy" which most major companies seem to have these days?
Apart from the combination offers, the staff always seem to be offering you some crappy reduced price chocolate at the till - yes, if I wanted the chocolate I would have already picked some up so sod off! Frankly their selling techniques feel like a petrol station these days.
Rant over