I have now sorted out the problem of the greyed out Bandlab Assistant with the cycling Windows logo. Here is what I did:-
1. I uninstalled Bandlab Assistant (from Control Panel)
2. I manually deleted two bandlab assistant folders that were not deleted by the uninstall process. These were located in users/(username)/AppData/Roaming
3. I installed BA 3.0.9 again
Now Bandlab Assistant opened properly and I was able to log in as normal