Thanks for the advice
 
I tried alt control F1 which gave me a command line - and allowed me to log in to a console, however, as I was typing the commands, it then automatically went back to the graphical interface. I then loggin in using the recovery mode which allowed me to run the
sudo aptitude update
sudo aptitude dist-upgrade
 
this seemed to run until it listed a syntax error with "freemed" which might be an application I tried to install in the past - it then exited back to the command line.
 
When I rebooted, it gave me the same screen - however, it tried to go past it, the screen would flash blank then white and then back to the cream blank screen. Eventually it popped up a box with:
 
"The greeter application appears to be crashing - attempting to use a different one"
 
After I clicked OK, the same thing happened - eventually sticking on the blank cream screen again.
 
Any ideas?