I managed to mess up a booking. Going to London for a weekend the 24-25th of November, and booked the hotel room for the 23th...I really don't get how I made that mistake. To make matters worse, I booked a non-flexible one, and the website showed the 24th as fully booked.
Still, I send an e-mail, asking if there is anything that could be done to at least partly fix the mess I got myself into...and they moved my booking to the 24th for a 10 pound surcharge.
TL,DR: booked a room at a 'fully booked' hotel by booking it for the wrong night first.