No. I've been aroud talking to the neighbours, spammed Twitter and Facebook and of course hunted a lot in person. I've called the nearest shelter, but because the cat's chipped, if he's handed in anywhere then I'll get him back straightaway, so I don't need to call the others. They've told me the location of some feral colonies near here, so tomorrow I'm going to see if he's there.
I'll also be getting some posters and flyers tomorrow and then widening the neighbour search, partly to ask for help and partly in case one of the them's 'adopted' him. And I've put food outside, though if he were right outside the house I'm sure he'd have just come to me when I called for him.
He's very, very attached to me; I don't think he'd actually want to leave - he probably fell off the windowbox, the clumsy animal, and then managed to make his way out but couldn't get back in.