You said, "the rad is basically on the side of the case with loads of vent holes o and the thermal paste is as3".
I would cut out ALL of the vent holes and eave one big hole. you problably have alot of backpressure of the air moving though the radiator AND small holes. Ideally just like you want enough water going through the block to cool the cpu, you want enough air going through the radiator to cool it also.
And te other guys are right. Reseat your block.
Take your waterblock off and put it back on. It may not be making good contact. Also be SURE to spread your AS3 out very thin. You don't want much. You may have put too much on and it's insulating instead of conducting heat.
Also what kind of equipment do you have? It sure would be easy for us to diagnose if you had say a weak pump, or a small radiator. or mab just a waterblock that sucks!