Since finding the Scarce Swallowtail pupa on our garage wall last winter, I'm more alert to creatures that use our house as a shelter. However, it was still a surprise the other day, to find that what I first thought was bird dirt stuck to the outside of a couple of windows, are, in fact more cocoons.
Each is about 2cm long, and what's so intriguing is that they're made from bits of plant material. What I believe is metamorphosing as it sleeps inside, isn't nearly as magnificent as the swallowtail, though. I think the (curious) common name is: Bagworm Moth (psychidae family). If so, the emerging moths will be small, plain brown and not terribly welcome if their caterpillars infest certain plants next year. Nevertheless, I'm disinclined to get rid of them - not least because they give me the perfect excuse not to clean those windows for months!
Update 23/10/2016: This afternoon there was no sign of the gekko, but what did I see when I looked up from the laptop?
I decided to take the opportunity to move him off the window and onto the window ledge, thinking that if he wanted to climb higher he would get a much better grip on brickwork than glass. I'd be doing him a favour.
At the approach of my hand the caterpillar jerked back indoors and froze, hoping to fool me that he was just another unremarkable scrap of leaf litter. The tiny bits of plant felt paper thin between my fingers. Too much pressure and I'd squash both house and inhabitant. Carefully, I laid it down against the wall, and stood back to watch.

About an hour and a half later, he had got to the top of the window. A journey that would have been so much quicker without my helping hand!
The last time I looked, he was still moving.