It gets hot from the underside, which I can feel when I put my hand under the chassis, so I tried to find out what was sitting there inside to be causing these temps considering this is a pre amp and not doing any hard wakka as such.
As it turns out, this is sitting there, the power supply:

And these are the caps in that power supply

So I'm guessing the 4 black transistors (?) that are attached the the chassis are what's causing the heat and they are using the copper chassis as a heat sink.
So my question is, are the parts pictured, and I know it's not detailed, good enough parts to be able to withstand high temps for a good while, I'm always paranoid with high temp gear, even though my Yamaha z9 will burn your hand at idle and it's lasted 12 years.
Any thoughts on the matter @Zaphod Beeblebrox
Cheers
I'll he to add, not a bad power supply for a pre, I've seen smaller caps in some amplifiers.