Steam headcodes on Met and District lines

Hi all,

I'm currently working on virtual models of the Metropolitan A class and related District locos for the Trainz railway simulator. I'd like to give them selectable lamp head codes, but can't find any information on what codes were used. It seems obvious to me that codes were used (why else would there be so many lamp sockets?) and also that the codes changed as the number of lamp sockets seems to grow with time. Does anyone here know what codes were used or know where I should look to find this information.

Thanks,

Ed