As the question says. I have a bunch of them but they let me play my backups for a bit then give me a dirty disc / disc unreadable error. Also can anyone recommend a good site in the UK that i can get media from and what media to get? Thanks to all help in advance.

HP=CMC Magnetics which like virtually all D/L media are very dependent on your 360 DVD-ROM/Firmware and your Burner/Firmware. The D/L media that has proven to be most dependable is Verbatim. http://www.svp.co.uk is a highly recommend site to buy from and they have reasonable prices on Verbatim. Some people complain about the higher pricetag as compared to other media, but then again even the cheap D/L aren't cheap if you are producing coasters and in either case it's still significantly cheaper than buying another original disc.