Ok. So setting fastboot mode from the diags menu seems to work. On my mac I now have the device showing as 0x1949/0xD0D0.
I have downloaded android-sdk_r17-macosx.zip and ran the android program within to install platform-tools, which contains the fastboot program.
In the dir of the fastboot program I do 'sudo ./fastboot getvar serial' which just sits at <waiting for devices>.
What am I doing wrong?!