Chose the slower of two shipping options I offered despite knowing that their schedule wouldn't allow them to be in to pick it up.
Messaged me one day after the delivery attempt (I used tracking and this was uploaded to eBay the same day I despatched) wondering where their item was. I showed them the tracking and explained about picking it up.
Then opened a claim against me "just in case" because the item went to their Post Office and apparently Royal Mail didn't leave them a "you weren't in" slip, and that they understood it wasn't my fault (said this twice!) but they "still hadn't received their item".
So basically, deliberately chose slow shipping, then blamed me for something that was entirely their responsibility (being in/receipt of the item) and opened a case against me when I'd done nothing wrong.