def canvasReleaseEvent(self, event):
    #Get the click
    x = event.pos().x()
    y = event.pos().y()

    canvas = self.canvas
    canvas.mapRenderer().setProjectionsEnabled(True)
    canvas.mapRenderer().setDestinationCrs(QgsCoordinateReferenceSystem(27700))
    espg = canvas.mapRenderer().destinationCrs().authid()

    point = self.canvas.getCoordinateTransform().toMapCoordinates(x, y)

class PointTool(QgsMapToolEmitPoint):
def __init__(self, canvas):
    QgsMapToolEmitPoint.__init__(self, canvas)

def canvasReleaseEvent(self, mouseEvent):
    qgsPoint = self.toMapCoordinates(mouseEvent.pos())
    print('x:', qgsPoint.x(), ', y:', qgsPoint.y())