Go to the Console to delete your LVs.
Ctl-Alt-X
Select Remove LVs (Logical Volumes)
After saying 'OK' to the warning, and entering the Console password, you will see a list of the LVs in your system.
Select the LVs you want to remove by highlighting them with the arrow keys, and using your spacebar to select.
Click Apply.
Exit the console when completed.