Ok guys, First of all i want to thank everyone for their advice, especially CarbonMonkey whom has tried to help me from day one....I really appreciate it.
Now please accept my apologies as this is going to sound like i'm going against you guys, but i believe i've already solved the problem:-
After carbonmonkey in a previous post told me that i may have possibly put too much pressure on the gpu by bending the x-clamps, i took everything out (CPU &GPU heatsinks) again, cleaned off the AS5 thermal paste (for some strange reason this paste has given me problems in the past too with PC building and heat issues, so i've binned it). I then reapplied new Zalman Cooler Thermal Grease CSL 850 and then sorted out the x-clamps a bit more straight and level.
I've been running the xbox and playing games since approx 6:30pm and its still working, so maybe i don't need to take drastic measures....at least for now? FYI, before the cpu temperature was absolutely boiling hot and after 2 mins i could not touch it and the console would go into 2 RROD. Now the cpu temperature has dropped to a level that i would say is only slightly above luke warm.