We stumbled across a really cheap company on ebay , that were only a mile from my house . They're a bit of a pain to deal with , but worth the effort for the cost saving.
I did the roof on my wife's workshop , and when we went there to collect the sheets, he'd got some 10' x 3'7' sheets left over from a job , and I'm sure that I only paid about £15.00 each for them . He even threw in a couple for free. He also had ,grey , box profile sheets , that were left over , and I think that they were about a tenner.