Hello once again good people.
The problem - whilst investigating another - what I thought was a problem but turned out not to be - I accessed root in Dolphin and noticed the file "dead.letter" which is 11Gb in size! I searched around online and found out about it holding some sort of messages but I don't know how to access the file to read them, or even clear the entire file to free up that space on root.
Any assistance greatly appreciated.