I have just uninstalled and reinstalled Security Center for a third time because I was still having DAT issues.
It has now installed Security Centre 12.1. It that the end of my out of date DAT issues?
One thing though, I does seem quite heavey on the RAM. I'm often using 75-80% available memory of 4GB RAM. Is this normal?
Yes that should be the end of your DAT issues because this version and upwards no longer uses them. Also note that one can no longer do the longer manual update from the McAfee download page that was previously possible.
The RAM usage should subside but try playing with the Real-Time Scanning options if you wish. Otherwise if it doesn't subside after a short while I would ask technical Support for advice.