I took the Socibus through bus option from Seville Plaza das Armas to Madrid Barajas via Madrid Estacion del Sur in late November.
It takes just over 6 hours.The bus may stop for a 10 minutes or so at Estacion del Sur awaiting arrival of the Socibus Service from Cordoba. There is a 20 minute stop en route near Bailen for food and watering.
The www.socibus.es currently shows a 01:00 departure from Seville arriving at Madrid Barajas at 07:30.
I would not recommend the Madrid Metro from Estacion del Sur or Atocha if you are in a hurry as it requires 2 changes en route and when you have bags it is a pain.
On my return trip, it took me 50 minutes at 06:00 in morning to get by Metro from Barajas to Estacion del Sur as the Socibus service had not yet started from Barajas.
