You can get 2 stackable plastic storage boxes for £3.99 at Lidl from Monday 10/03/14, there are various colours to choose from and they come with a 3 year warranty included as well.
Product Information :-
Ingenious stacking system allows boxes to be stacked on top, as well as stored inside one another
Capacity (L): 15
Size (cm): H20 x W28 x L38
3 year manufacturer's warranty