Well...heres an update for anyone that maybe interested.
I phoned Sony. They passed the buck, sed it sounded like a problem with the game, so advised me to contact Activision, who make the games.
So i did that...spoke to a guy who suggested trying the discs on another ps3. I tried on my neighbours and all worked well. So the buck goes back to Sony.
On Sunday, i again phone Sony, explain the situation to them and they suggest that i would need a replacement ps3, which they could provide (recontioned) for £110. I thought sod that, Sony are making a killing, buy getting me to buy the original PS3, then the replacement and in the meantime, they get my "faulty" ps3, to do up and then sell on for another £110,so on principle I decided to not take them up on their offer.
So, i went and bought a new one, got home...set it up....and lo and behold, the problem is still prevalent.
So i contacted Sony and told them the situation. Im really hacked off that they suggested my PS3 was faulty, which made me think i needed a replacement. NOW Sony have changed their tune, they are trying to suggest that it might be an internet problem, and that i needed ports open on my router. So i contact ISP and they stated all the ports are open.
So thats the state of play. Im stuck with a brand new ps3 i didnt need. Strange thing is...my sons ps3 at his home is also not playing on MWII. So isnt it strange that 3 different machines on two different networks are having the same problem?