Yep, go see the site manager, but WFP is no good for an initial clean, you may have all sorts of rubbish to get off the glass, putty/paint/silicone/sand & cement and so on.
So if you want the initial clean, make sure the scafolding is still up (preferably)
Else you will have to do it off ladders, and if that is 3 storey, then there may be H&S issues regards WAHD. As it is 'on site' these are frequently adhered to strictly.
For the repeat clean, keep calling in as the place is being fitted out for whoever is moving in there (if any one is of course)
Or ask the site manager who to contact with regards to the regular clean, it isn't always obvious as the owner of the building my be renting out different floors.
I have a couple of offices like this, I have to bill an estate agent who is responsible for the buildings upkeep, in the one office, the top floor is empty, the first floor has an architect in there and the ground floor is a solicitors. I've never even met the buildings actual owner! and I've been doing this particular office for 18 years
Beware the initial clean, if it isn't likely to lead to the regular clean, make sure you price it well, I personally charge 3 times the regular clean price, if I know it is going to lead to a virtually guaranteed regular clean, then I'll put a tighter price in, as so far I have found office blocks make me way more money than any other type of clean I do, and by a long way too.
So it is worth it for me to be tight on the initial clean.......but that doesn't mean so tight you are making a loss
On the repeat cleans you are spot on with regards WFP, they really come into their own on this type of work
Ian