It depends on what you want to do it for, if it is a temporary thing then you can simply flip across the bear claw catch of the lock to simulate the flap being closed, we do this when trying to follow parasitic current drains when we need the drivers door open but the car to think it is shut, all you have to do is press the boot catch and the lock will flick open, some cars even have a orange topped lever on the lock for this, not sure on the latest Polo. If you need it open for something like fishing then you could consider changing the light to LED to reduce current consumption to virtually nil and still be able to find the sandwiches and coffee flask.