Not sure of the specifics, but as far as I can see practically everything is cheaper in the north ( apart from the well publicized exceptions like cigarettes & petrol).
Best buys I would guess should be with the higher priced electrical stuff (from DVD players/hi-fi to fridges/cookers). You should get good value on most most furniture and furnishings and in my experience there are always savings on luxury food items. The south is a bit more competitive with booze prices these days.
A word of warning - always be highly aware of the true ST/Euro comparison. Don't rely on a rough estimate because you'll find that you will unconsciously kid yourself into 'bargains'!!