It seems to be the time of year that Ladybirds decide they've had enough of being outdoors and crawl through our open windows to curl up in the corners of our nice central heated rooms. I've found quite a few around the house, of various sorts but mostly Harlequins and Seven-spots.
There's more information about this autumnal habit of Ladybirds courtesy of ladybuglady.com. They emit a pheremone that attracts more ladybirds so you can end up with masses of ladybirds clumped inside your house, which may emit a bad smell and stain the walls. I get the impression that the Harlequins can be a particular nuisance.
The picture above is a Harlequin as evidenced by the big black M on its head and the orange legs.