I find the render I've come accross one of the hardest things to drill . A
normal hammer drill was pretty hopeless even on small holes whereas SDS
makes dust out of it.

You are not joking. I have drilled render with a 5.5mm drill on a SDS
machine and had to insert a brown plasplug to make the screw fit tightly.
From now on it is 4mm drill on render and I will work up to a 5.5 mm hole.

--
Adam