Windows Deployment Server - Clients not taking new Hostname

I have set up a Windows Deployment server on Windows Server 2012.

It is set up to allow any client but requires an administrator to approve the request on the server. I have successfully captured and deployed various images from it.

The only problem I'm having is that if I prestage a computer or use Name & Approve then although the requested computer object is created in AD the actual client doesn't use that name but instead defaults to using the username based template eg martin-3BTU3AT6

I guess that there is an issue with my unattended files somewhere.

I have attached both of the files here: http://pastebin.com/rkRKh2Lk (With personal data replaced) I'm sure there are ways that they could be improved, I put them together with the help of a few online tutorials that seemed to be doing similar things! (The local account is there for testing only and wouldn't be included in production versions)

Any advice would be greatly appreciated. Thanks, Martin