Expensive. Look up steel stockholders in your area and see if they have a rummage bin. For stuff like that, locally, I pay £0.85 per kilo. Even if you paid a cutting charge, I am sure it wouldn't be that much.
Its going to be £10 of anyones folding from anywhere..... but then if its ebay, probably another £10 carriage....plus the other £5 to cover his ebay fees, paypal fees.....
Just put it into an online steel stockist shop, comes in at £34.73 delivered
It's worth asking around for a small steel fab business,I found one that had been there years,and I'd just driven past.
He's a gem,sells me 6M lengths of angle at about cost,and cuts it at 2M or 3M so I can put it on the roof bars.There's a big bin of off cuts inside the door,if I want a bit of plate,I just stick my head round the office door and he says have a look.
Just a thought,if you're near here,phone them for a price.As said,delivery will be as much as the steel.