Do I have to remove the existing Sparky version or can I just install over it hoping for the best.
You do not need to remove existing Sparky version before installing a new one.
Simply use APTus-> Desktop to choose and install a next desktop to be tested.
Thanks Pavroo tried xfce through Aptus nothings changed. Same as before.
After installing a new desktop you have to reboot or logout and log in back.
Then choose a new desktop from a list which is available in the right top corner on the login screen.
Did you do that or just re-login without changing the desktop?
:( Just logged n out sorry :P