I would use the "Broadcast Colors" filter in conjunction with the levels filter, as they do different things.

The levels filter can adjust black and white levels... i.e. to make your images look better.

The broadcast colors filter can clip or roll/smooth off illegal colors, which the levels filter cannot do. I'm unsure if it gives perfectly broadcast-legal colors (I'm not a video engineer). It may not for PAL. Anyways that's an area where my knowledge is sketchy on.