Bear in mind the chains weren't as cheap as I expected. I probably spent as much on chains as I would have on the same amount of plates. The plates I had were 2 x 0.5kg, 2 x 1.25kg and 2 x 2.5kg, so consistently small increases were impossible for me anyway.
The chain was from B&Q. I think it's the 6mm one. The links are 2" in length. 20 links weigh 538g.