f Can the SiteWorks team help if our WordPress site is hosted on our own site? 

Of course.  Any services provided by the Trust are available to all u3as.  However, the assistance would be limited to the use of the theme and plugins developed for, or selected for use with, the SiteWorks WordPress implementation.  It will be unlikely that the SiteWorks team will be able to help with issues such as hosting or email.

For issues outside this scope, the u3a WordPress Development Forum (you may need to register) provides access to more expertise and a SOS service.