Managed to find out the cause of the overheating. The laptop has a Nvidia Optimus enabled GPU setup. This means it has an Intel GPU and an Nvidia GPU. On Windows it automatically switches between them. With the out of the box drivers on Linux both run at full tilt causing all the heat.
There is a driver package called Bumblebee which resolves this. All running nice and cool now.
If you'd tried Manjaro as I suggested earlier, you'd still have the same (but more up to date) Cinnamon DE and it would have auto installed bumblebee for you (as I also mentioned).
Glad you got it sorted mate.
BTW, OhEsEcks I know it was an oversight but on Debian/*buntu distros the command you listed (sudo apt-get update) would only refresh the index. You'd need sudo apt-get upgrade to actually perform the updates. Or, to make it simpler, sudo apt-get update && sudo apt-get upgrade. Just in case anyone followed it and was left scratching their heads.
OP, don't do this on Mint though. Using apt-get upgrade leads to borkage on Mint systems. Another reason I prefer to avoid it.
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