m17xr3- gfx card 580m extreme throttling

Hi all.

I've owned a m17x r3 for a year now that i purchased and shipped to myself, at the time living in Australia, where i frequently enjoyed Skyrim on modded to beyond Ultra (whilst sitting with AirCon freezing the room out of preference). I've been living back in the UK since April and in in the last few months I have struggled to run anything on settings higher than Low on all the games i play except Minecraft and Solitare. Throttling  to between 1-10 fps on when on Low settings is common for me on the following: MassEffect3, BattleField3, Skyrim, StarCraft2, LeagueofLegends, Dota2, Firefall.   I purchased a Coolermaster notepal U3 stand to try and fix the problem but it's affects are far, FAR,  from running any of these games on their top spec. If i were to play Skyrim i would spend 1minute playing on Low, and 1 minute waiting on menu to cool.

Noteworthy causes/possibilities;

• I am using a non-provided wall plug to connect the charger-brick to with the wall socket (the generic 3pin monitor style power cable.)
• Overclocking the fans to an ungodly speed to keep it all cool.
• It's widely acknowledged that the 580m heatsink pre-November '11 is faulty and ineffective.

Having owned a few overclocked PC's previously I'm not new to spec tweaking, but this is currently unacceptable. I don't want to fiddle with fan speeds settings in fear of breaching the warranty with some undesired consequence. Preferably I would like some confirmation about the heatsink and get it replaced with a fully functional one (Since it was bought from the US and i live in the UK I'm unsure how to proceed), allowing me to enjoy the quality that was paid for.

What would be my options to remediate this problem?

Kind Regards,

Chris