Forget all of the flimsy or ridiculously expensive storage boxes you have previously come across and instead buy these fantastic indestructible boxes made by a British company called 'Wham Bam'. You can stand on these blighters and they will not break!
They come in all shapes and sizes and the best price I have come across is on Free 'click and collect' from the ASDA stores website ( see link below) .They are made from super thick recycled textured plastic in a nice neutral grey colour . I went for the stackable 36 litre 'under bed' type boxes at only £9 each.
https://direct.asda.com/george/clothing ... %20Upcycle