Right, update:

I took the PS2 back to the modding shop and he told me (after keeping it over night) that the laser wasn't strong enough to play copied DVD-r games. He offered me a new laser for £45 pounds, but warned that it could burn out the PS2 in a month or three as he reckons PS2s have always had very poor lasers and a fault in every model that they are trying to remove at Sony but never manage to do so.

I can play CDr games, DVDr movies, but not DVDr games. How annoying is that.

Well the end of it is that I can't play the games I backed up, so my originals aren't safe after all

I'm thinking of selling this PS2 and then buying a pre-modded one from somewhere else, see if I have any luck this time...