At least one of the birds pops in regularly to have a look around and to rearrange the few bits of moss and grass.
Here is a mouthful of moss coming in this morning. Things should speed up now that the weather is warm and dry.
Just now the box was visited by a bumblebee queen who checked it out for a few minutes then left. As far as I can see it was not a tree bumblebee (Bombus hypnorum), the species that typically nests in bird boxes, so it may have just been inquisitive.
There is now a separate page, accessible via a tab below the header photo at the top, which will give more regular updates on the nest box.