Help! Im about to drain my central heating system and need help about the drain valves.?

Im about to drain my central heating system. Im 99% sure i have an unvented system. I have so far: Turn off the stop and check no water is coming out of the cold tap. Turned off the back boiler and emptied the cylinder of all the water. Made sure the emersion heater is off. and turned off the turny thing my plumber told me to turn. Now im stuck. Everything i read says to attach a hose pipe to the drain valve...I cant find a drain valve anywhere! 100% sure the system doesnt have one. So now what do i do??? Help please!