Wilco's made the decision for me - advanced trap (I can't resist a gadget !) They did have poison but I did not want to encourage the flys....
The 'advice' says use chocolate, so I have off loaded some of the responsibility and eased my conscience. So its me and Andrews buttons (and some self responsibility from the mouses for pooing in my pan cupboard) - at least they will go with a nice taste in their mouths :-(
I feel bad already !