Update....
Stripped down the PS2 to give it a good clean, especially the laser eye. When I put it back together I tried a couple of PS2 backups (DVDs) and it worked fine !!!!
But after 5 minutes of playing and trying to load another backup it went back to not accepting PS2 backups again.
Originals and PS1 backups are fine still.
What is going on ? Do I need to strip it and clean it all the time ?
The laser test tried above indicated that the laser was OK.
Please help !!!!!