Do you have a leaseholder application process detailed in the building freehold? If so, what are the particulars of this?
Ultimately, you need to establish what works are taking place now, and what the statutory processes are for these works. Freehold agreement particulars excluding, could your neighbour just be doing internal works that don't require a party wall award?
Again freehold agreement particulars excluding, it is worth noting that your neighbour can do non-notifiable works without the party wall award in place. Maybe your neighbour's contractor is just trying to get ahead of the works thinking the award will come through during this period. Pretty brazen, and the party wall process can be pretty drawn-out information/neighbours/surveyors depending.
Communication is obviously key and clearly, your neighbour is lacking in this. It is worth teaming up with the other leaseholders/properties to help apply pressure on your neighbour/contractor to establish the current works and future works programme.
For reference, Permitted Development rights do not apply to flats, so any external works (moving windows etc.) will need planning permission which clearly has not been approved as yet.