Moving from your subject to SEN teaching is done 'on the job'. My advice would be, once you gain QTS, to complete induction and in your first post induction job let it be known that you would like to specialise in SEN. Then ask for training opportunities in SEN and for opportunities to work with the SEN department. Gaining this on the job experience will, by then, be second nature for you as a GTP. Your priorities now should be to gain QTS then pass induction with a view to moving towards SEN. James