...I think that at the moment, just for streaming, iPlayer uses about 60Gbps of bandwidth (that's about 7.5GB downloaded every second) in an evening peak. I think about 15Gbps for downloads and about 1.5Gbps for iPhone. So overall on a particular peak day we may hit 100Gbps (about 12.5GB per second) although typically it'll be somewhat less than that. That turns out to be up to 7PB of data transfer a month.
BBC iPlayer boss Anthony Rose, in an interview with CNET UK.