Note: This solution is only applicable to version 10.x, version 11 doesn't use advCustHelp.
The default logon page for the Access Policy Manager module is pretty basic, particularly so if only the...
Top tip - if you want this to be saved in the UCS file do not edit the file on the box. You need v11 to do this (I'm on 11.5.1)
Great page - used this to allow user to choose between split tunnel VPN and Full VPN.
In Access policy on the GUI go to Customisation --> Advanced
Select edit mode (as opposed to properties)
Then go to Access Profiles --> /Common/{Access Profile Name} --> Macros --> {Resource you applied policy to} --> Logon Pages --> Logon Page --> logon.inc.
Edit and save there.