Problem with QDockWidget

[Banjo]

Hello
I am new to QT and am having the following problem with a simple test application that I would appreciate a point in the right direction.

I have used the Designer to create the interface as follows:

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(QtCore.QSize(QtCore.QRect(0,0,800,600).size()).expandedTo(MainWindow.minimumSizeHint()))
 
        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
 
        self.line = QtGui.QFrame(self.centralwidget)
        self.line.setGeometry(QtCore.QRect(663,50,20,481))
        self.line.setFrameShape(QtGui.QFrame.VLine)
        self.line.setFrameShadow(QtGui.QFrame.Sunken)
        self.line.setObjectName("line")
        MainWindow.setCentralWidget(self.centralwidget)
 
        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0,0,800,21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
 
        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)
 
        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)
 
    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(QtGui.QApplication.translate("MainWindow", "MainWindow", None, QtGui.QApplication.UnicodeUTF8))

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(QtCore.QSize(QtCore.QRect(0,0,800,600).size()).expandedTo(MainWindow.minimumSizeHint()))

        self.centralwidget = QtGui.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")

        self.line = QtGui.QFrame(self.centralwidget)
        self.line.setGeometry(QtCore.QRect(663,50,20,481))
        self.line.setFrameShape(QtGui.QFrame.VLine)
        self.line.setFrameShadow(QtGui.QFrame.Sunken)
        self.line.setObjectName("line")
        MainWindow.setCentralWidget(self.centralwidget)

        self.menubar = QtGui.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0,0,800,21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)

        self.statusbar = QtGui.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(QtGui.QApplication.translate("MainWindow", "MainWindow", None, QtGui.QApplication.UnicodeUTF8))

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with the main file:

class MainWindow(QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)       
        self.createDockWindows()
 
    def createDockWindows(self):
        dock1 = QDockWidget("Dock1", self)
        dock1.setAllowedAreas(Qt.RightDockWidgetArea)
        w = QLabel("Hello")
        dock1.setWidget(w)
        self.addDockWidget(Qt.RightDockWidgetArea, dock1)
 
def main():      
    app = QApplication(sys.argv)		    
    mainwindow = MainWindow()
    mainwindow.show()
    sys.exit(app.exec_())
 
main()

class MainWindow(QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)       
        self.createDockWindows()
               
    def createDockWindows(self):
        dock1 = QDockWidget("Dock1", self)
        dock1.setAllowedAreas(Qt.RightDockWidgetArea)
        w = QLabel("Hello")
        dock1.setWidget(w)
        self.addDockWidget(Qt.RightDockWidgetArea, dock1)
                       
def main():      
    app = QApplication(sys.argv)		    
    mainwindow = MainWindow()
    mainwindow.show()
    sys.exit(app.exec_())
    
main()

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The problem that I have is that when the dockwidget is resized by the user, it just goes over the top of the main window. I have tried writing the interface manually and that works but I can't work out why using the designer is different - obviously some operator error but I can't work it out.

Thanks in advance