For boxes Staples normally have the 64L Really Useful Boxes at 2 for £20 (or £17 each!). I use those and 35L ones (£7 from Costco) for all my work stuff as I need secure boxes for equipment (but can’t afford Pelicases).
For bike stuff I use the clear Ikea ones which are okay if the place you are storing them in is dry as they are not as well sealed as RUB.
Not compared them to Big Dug but if you can get to Costco then worth a look as they have some pretty damn solid black steel racking, large chrome wire (like you see on Masterchef etc) and also a smaller version. We have a couple of the smaller chrome wire set ups as they don’t take up much room. They might be a bit small for a garage though but they are about £20 a set.