Unable to import data from Membership Premium to Membership Pro 2

Hi there, I am trying to upgrade an old site from Membership Premium to Membership Pro 2 and it's driving me nuts!
I don't see an "upgrade" option in the WPMU DEV dashboard so I have tried to install MP2 on top of the old MP by clicking "install" in the dashboard - this results in an error that file permissions are incorrect.
I then follow the instructions and deleted the old MP files via FTP and installed MP2 via the dashboard and it installed fine - I see the import screen but not matter what options I select the process just hangs?
Nothing is imported and there are no error messages - it just hangs with the import bar at xx% and does nothing???