I would say this is not a Biscuit Beetle - it doesn't have the right proportions for that kind of insect. I think it is a Darkling Beetle (family Tenebrionidae), but I can't say what species. It could be one of the Flour Beetles Tribolium sp. I really don't know, but I think this is the family you should be searching into. You could always send us a few specimens for an ID:
Identification and Advisory Service The Natural History Museum Cromwell Road, London SW7 5BD
Please us a rigid container to protect the specimens from being damaged in the post.