if you control the work and the hours and give them the equipment they are not self employed, u might try a cscs card which is a bit like self employment but u still have to take tax off them
if they use there own van, tools, and just rent the work off u or invoice you for hours worked then they are self employed
a lot of taxi drivers hire the can/box for a set fee and are then self employed as they can work what hours they want
if u decided to fiddle the self employment and HMRC catch u then u are liable for it not the employee as all he has got to say is i thought the tax was been taken out, he might have to pay the tax, over the following years but u r the one who gets fined for fraud and poss prison