How to Publish Exchange 2010 OWA and hide public\private computer option

I need to remove the public option on the OWA login page so users are only left with the option of "this is a private computer".

The following thread asks this question: http://social.technet.microsoft.com/Forums/en-US/exchangesvrclients/thread/06efc14c-1146-45a8-b364-98339500a1ce

Derb's blog has a suggested solution http://blog.leederbyshire.com/2012/11/01/how-to-remove-the-public-or-private-radio-button-in-microsoft-outlook-web-app-2010/ 

Derb's blog didn't work for me (made changes, restarted IIS and no luck). I also tried "style=display:none" rather than "input type=hidden".

I suspect that when publishing OWA using TMG 2010, the logon.aspx isn't being used on the Exchange Server. However I couldn't find an equivalent login page on TMG. Has anyone managed to get Lee's suggestion to work with TMG?

Thanks

IT Support/Everything