Sucess
 

Well guys it worked but I had a bad moment when I thought it had not as I will now explain.
I did the speed tests and opted for 100M block size (15seconds). On my calculations this would take 3hrs 20 mins for the 80Gb disk. I used the dd command as discussed earlier and went away. After 4 hours the disk activity lights were still on and the disk were spinning. After 8 hours I decided that it must have all gone wrong. The cursor in the terminal window had not moved at all, so I killed the session and went away to have a think of plan B. A few hours later I ran up Knoppix (CD) again and after it had loaded I noticed that it was now showing two partitions on the new disk. On investigation I found that the files on both the disks were identical. So, tongue in cheek, I popped the new disc into the PVR turned on and waited for the error messages but to my complete surprise it booted up and worked ok.:newbie:
So anyone any ideas as to why it appeared to hang ?. There were no bad sectors on the new disk by the way.
So a big thank you for all your help and comments once again.