I'm not sure any of it really matters, if it was good enough and you thought it worthy you would have paid, you don't, you're not, job done. Someone else might, maybe they're richer than you, maybe they view that cottage and that location as more important than you do. There's no right and wrong, this isn't mass murder.
you might be surprised at their ability to rent it out this late in the day – lots of people don't even book stuff beforehand, they just drive around asking for spare rooms.
Indeed, I@ve done this before – not had plans to do anything but decided last minute. Even when camping its rare to find a site that isn't rammed to the limits despite being bookingless 2 days before.