Sometimes there isn't really a problem just an issue ...!
DOH..
All good now and the 9.8 upgrade is really slick (have NetApp finally made a usable piece of software ....?). Many times in the past I've had to tinker with the VSC admin mode command line, force removal of plugins from the VCSA via the /mob or use some other KB to get it going.
10 vCenters all upgraded without a problem at first time of asking..!
cheers P