XP Remote Asistance – admin permissions

I am looking at using XP remote assistance for fixing 1st line faults for 1400 users, some very remote (XP is about to be rolled out on all client machines).
All the literature I have read on RA tells me that the permissions on an assistance ‘session’ are determined by the end user’s permissions, not the administrator’s. As group policy is going to lock down the user’s desktop, this makes providing a fix very difficult unless the helpdesk can take control of the PC with the appropriate admin rights. Any suggestions as to how the helpdesk can achieve this?