Easy peasy when you know how.
Boot up to safe mode - run this : http://download.nai.com/products/mcafee-avert/tools/SDAT5958_EM.exe
(In some instances in safe mode the start bar was still missing, so put a my computer icon on the desktop to access memory stick this way. Use either command prompt or ctrl, alt, delete task manager to restart system.
Boot into normal mode. Run Mcafee updates.
Whilst updates are running you'll get the worm like prompt that your system will be shut down in 60 seconds.
Go to command prompt - type shutdown -a. (this can pop up a few times during update - so you'll need to do shutdown -a each time)
Allow Mcafee to finish installing updates.
All fixed.