UPDATE:
Right, well the fan started making an odd noise the other day.
To cut a long story short, I traced it to the fan itself. The bearings needed to be oiled (which I did - quietened it down massively).....
.....but whilst it was all lying open and disassembled, I decided to do a further minor mod purely for a laugh
:
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...yes, I know, adding an internal light is completely useless but it's fun to do all the same
.