Ok, so I realise that the aBit uGuru panel isn't the most accurate temperature monitoring tool, but when it's reporting my CPU as 17 degrees and my PMW is reporting 52 degrees even I can tell somethings not working properly.
I suspect it's due to the case design as there's a dead spot of airflow right by the back edge of the case and if the PWM is what I think it is (largeish heatsink by the CPU socket) then there's very little airflow getting to it, despite the additional fan on the side.
Any suggestions on how to get some more air to it?