Posted: 21/05/2017 at 19:43
They're probably Tree Bees ... they often nest in bird boxes. They're fine ... not at all aggressive and good pollinators so good to have around the allotments.
They'll move on of they're own accord at the end of the summer.
There's nothing you need do other than enjoy watching them.
There were some in next door's roof the other year ... there were usually a few 'guards' who used to 'dance' around the entrace to the nest ...fascinating to watch.
Lots of interesting stuff about them here