With Flying Blue involved, you will have even more complications, as nobody might be willing to help you.

There is nothing wrong with looking at your alternative options now and calling Flying Blue to see about changing. But until the flight is officially cancelled you will likely have to pay change fees and stay within award space.

You can certainly wait until the flight is cancelled, and push VS to rebook you, as it would be within 14 days of departure and AFAIK it would be VSī problem to get you to LHR. But I would expect a lot of back and forth as VS and AF try to push the problem onto the other...