I've got a Makita set from screwfix £20 & it got loads of screw driver bits drill bits flat bits hole cutters the lot & some bits I don't even know what they are
How about SDS 5.5 x 160mm tungsten carbide double fluted shank cross head (4 cutting edges) £1.39 each
Like this one.. http://www.tradediscountshop.co.uk/shop/sds-plus-crosshead-drill-bit-5-5mm-x-160mm-concretecement/