I've recently found a website that wil convert the old "Modified British System" coordinates used in the IX Engineer Command history to true latitude/longitude coordinates. I've started converting them and have done the first batch. Here are the results ... http://snipurl.com/IXEC_Airfields
It is a manual process and I'm looking for an Internet and Excel savvy volunteer who might be able to help. If you are willing to help convert these then please send me a note and I can walk you through the process.