SamBeavis, Following up to see if the Dell Agent performed remote access to your system and work on the issue?   Dell Agent used remote access to remove all instances of SupportAssist and then was able to reinstall it.   
I've followed all i can in the community post around the same query to no effect (the post under 7389523, I cant put link as wont let me post with it in there)   I've downloaded all Windows updates When I try to install SupportAssist I get a message "This installation requires an internet connection. Check your connection and try again. If your connection requires a proxy, use the following link to review or update your settings"My internet is fine I don't need a proxy
SupportAssist will not install