if he worked for you doing your custys, he is not self employed he is employed, u could sub contract to him, but he would have to work for someone else 1 day a week to avoid the employment laws
if he got 10 custys him self for 1 days work and they subed to u 4 days a week he would be classed as self employed
u could employ him on a CIS card, but u would have to take 18% tax off him and he would have to sort out his own NI and u would have to give him vouchers for the tax u take