Thanks Steve for the reply.
I am still stuck on one part.
My surface pro 3 seems to load the \boot\boot_x64.wim fine from my PXE Representative (although it takes about 5 minutes). I get the following in Windows PE
x:\windows\system32>wpeinit
x:\windows\system32>wpeinit /unattend=x:\ldclient\setoptions.xml
x:\windows\system32>\ldclient\LDDrvLoad_x64.exe
The system cannot find the path specified.
x:\windows\system32>wpeutil disablefirewall
The command completed successfully
x:\windows\system32>reg import all.reg
The operation completed successfully.
The sytem cannot find the path specified.
The sytem cannot find the path specified.
The sytem cannot find the path specified.
The sytem cannot find the path specified.
The sytem cannot find the path specified.
Microsoft Diskpart version 6.3.9600
DiskPart was unable to open or read the script file.
Make sure the file you specified exists.
The system cannot find the path specified.
"No Corename set in corename.txt. Verify the wim file is valid."