Just found this for you Sue:
http://www.english-nature.org.uk/abo...BoxLeaflet.pdf
I think I'll give the two flower pot designs a go on our orchard allotment... Interesting what it says about mouse nests. Shorty PM'd me a while back about this, asking if I thought one of our pet rats' nests would do the same thing (her dad's setting up a hive). I have no idea, but I've posted her one anyway. Fingers crossed!