Just to correct my post a little; I put the cable ties through two guard holes (not radiator slots), you can see one of them in my pic. The bolt spacing at the bottom is 6 or 7 mm.
As you say Brockett and Zippy the two vertical sides of the radiator are not aligned but my guard sits just inside the lhs of the radiator body and passes the rhs by a couple of mm,viewed from the front.
Nothing wrong with the part supplied, just a slight bit of improvisation required.