This rather interesting badge recently appeared on eBay. I've come across some information on specific ARP teams attached to the various railway companies during the war but I have not seen many specific badges. There was a GWR ARP helmet that appeared sometime ago but the authenticity of it was questioned at the time. If you know more about ARP teams working for the railways please let me know.
News about interesting insignia, ARP related info and period photos that turn up.