Originally Posted by stut

There's a bus from CRL to central Brussels for €13, which runs until just before midnight, so you should be able to get that. From central Brussels, it's a short train journey from any of the major railway stations (South/Midi, Central, North) to the airport. There is also a shuttle bus from the airport to Charleroi Sud station (€2.70). You can then get a train to Brussels, and an onwards train to the airport.