Sorry I haven't got back, I actually sorted this shortly after. I was applying group policy and restarting straight after. I removed these steps and it sorted the issue. I've just incorporated your wnb.xml and it works a treat. Thanks again!
Just have some trying to smooth out some teething issues, had lots of problems with the PXE loosing it's boot files from the RemoteInstall \smsboot and some oddity where it can't create the folders on the C: drive when creating the USMT stores prompting incorrect function (Failed to run the action: Create USMT folder to store USMT packages. Incorrect function. (Error: 00000001; Source: Windows)) even creating the folders manually and I'm getting errors when trying to run the manually copied scanstate.bat (Failed to run the last action: Run x86 scanstate. Execution of task sequence failed. The specified disk or diskette cannot be accessed. (Error: 0000001A; Source: Windows)). I'm getting there and I can't thank you enough for your guides!