after my removal when and how should i return in uk

HI every one

i arrive en UK in 2005 i claim asylum and being granded discretional live to remaind until my 18 birth days en 2007 my aplication for for extention was turned down my asylum process restarted and being refused
i have been remove from UK in force in 2007 , i left my girls friend and my child behind she is still in the asylum process and has not yet grand ILR I have study in uk I have many certificats and diploma gained there
I am holding my national NI Number and my UK driving licence when and how can I aply for UK visa . i do not have none police criminal record

pleas some one give me a right answers