Looks like channel 5 is branching out not only with the new channels, but also a download service for all the favourite shows like CSI etc
Channel 5 downloads
It look's pretty good, but the pricing and timescale (access to the file for upto a period of fourteen days) looks to be a bit of a downside. I expect most die-hard fans would pay the £1.49 for previously shown episodes, or the £2.49 for unseen, unaired episodes.