I saw some suitable containers on the back of truck collecting waste veg oil from a chip shop.
Unfortunately I didn't have time to stop and try to relieve him of one!!
If anyone knows where they come from, I am after one as well.
We used to use oil from A&B (I think it's the one you saw). The oil come in 20 litre plastic drums. They are fine if the lid is shut, but once it's left open, the drum doesn't retain its shape very well.
I also have 20 litre metal drum, however, you'll have to roll the edge down with pliers/hammer as it's very sharp. They are rigid enough tho.