Also a big fan of storm blocks but the one thing here in favour of d-wax is the moisture content. I recently did a job in a fairly modern pig unit, all concrete panels rather than block work. The only place for the mice to live was the small cavity between the panels and plastic feed hopper.
They were basically living in the pig feed that blew over in to the cavity. The feed being a very dry powdery meal, the only reason they had to leave this spot I imagine would of been to drink. You could watch them coming up and eating the d-wax pretty much as soon as it hit the floor!