I'd been washing my dreads and the water that drips from the ends when you've got out of the shower with them accidentally scattered over the keyboard. I'd just attribute it to why keys stopped working, probably half an hour afterwards, and when I got up this morning none of the keyboard worked at all, and the mouse only right-clicked. Sorry about the inarticulate first post too; had to drag letters from the script around this page to type it! Ee, I've learnt something.
Will probably have to get a new iMac mouse-and-keyboard if anyone knows of a good place to quickly purchase them. Currently "borrowing" some.