Darran that reminds me of a job we did 5 years ago in Cleckheaton only yours looks like no more than a 2 day job.
All the rafters were caked in dust as it used to be a factory making brake shoes. We washed everything down and had a roadsweeper clean the ground. After we finished the painters went in.

Lee - That looks like the old Mintex place - my father and brother used to clean all the windows there and blow down the insides once a year!
Most of the dust used to be Asbestos back in the day so I hope you wore full breathing kit, unfortunately in the eighties the team of cleaners were given paper masks only

The external of the building took us less than two days pressure washing, but then we restored the powder coated window frames and lots of stainless steel - sun screens which you can't see on the pictures - this took time as we did this by hand, slowly.