The message
from "GB" contains these words:

I now want to put up shelving screwed to the walls.

Glue battens to the walls and fix the shelves to them. Provided you're
sensible about the areas involved you'll have no trouble at all. A
couple of 3' long bits of 4x2 well stuck up with no-more-nails-alike
will take loads of weight.

But, if you must drill it, get a cheap SDS drill (they're about £30).
It'll sail through it, and usually comes with a useful selection of
adequate quality bits.

--
Skipweasel
Pay no attention to that man behind the curtain.