more help on poorly disco

right, had a good look under the hood and i notice that the heater matrix hoses aren`t getting warm,would this cause my engine to overheat? also there seems to be a bit more bubbling than normal in the header tank, i also let the rad bung out and water with air bubbles is coming out is this my problem? air locked? whats the best way to get shut? i`ve tried bleeding it off but no sucess, i can`t undo the bleed screw on the thermostat coz b4 i owned it it has been replaced with a rusty rounded bolt(nice)