35L Really Useful Storage Box - set of 4 for £32 (£8 each) @ Asda

Not the most exciting deal at this time of year, but I've just fitted out my new shed with 12 of these.

Next cheapest I could find was £12 each.

Really sturdy large boxes with clips and lids.
Much sturdier than the ones we got from Ikea/tesco/b&q/etc
Fits A4 suspension files too.

Collect at store available for free.

They don't nest though - so when I collected 12 it filled every inch of our Berlingo.