tried installing dvd to another machine - no go.
Downloaded from Europe mirror instead of BT in case I got a dodgy download. Europe file said it was 3.9Gb. After downloading it is only 2.62Gb

Tried that as well on 2 machines and got I/O boot cd error msg.

Can people direct me to the mirror that they have recently used (ie in the last couple of days) that the installation was successful for them. I was downloading the single layer amd64 DVD iso
Use the torrent instead, it will check your download for you. And you can start with the partial download that you grabbed from the mirror already so you don't even have to start all over again. Mirrors will give you dodgy downloads, not the torrent.