Interesting...
I've no advice to offer, I used to do no end of builders cleans but no longer have an interest in them.
However it IS interesting to see that you now need tickets of certification in (I'm guessing) a similar manner that anybody self employed in the construction industry has to have.
Back in my builders clean days, window cleaners were not considered part of the construction industry and thereby were exempt from such things....times, they are a changing. (Or have changed I should say)