60 hour makeover

If you look very closely, you might see a wren's nest. It started it a week ago (or at least I first noticed the activity a week ago). Today it has been carrying leaves for hours. I think it's only one bird and didn't seem to stop to eat. I don't really know anything about wrens. Someone out there might be able to tell me more. Do they have more than one nest?

I'm quite worried about this nest because this is a south facing wall and in the sun, it is very hot. In the past the wren has nested in the clematis on the fence which seems much more sensible. We'll see.