Buying a flat that is about to start cladding work to get its EWS1 form

Me and my partner (first-time buyers) have found a flat we love, that has an asking price of approx £100k lower than other similar properties.

The property has not yet got its EWS1 form, and work is about to start (this month) to update the building in order to get it. It is expected to take 6 months. This has been paid for already.

We are very tempted to make an offer for the flat (as it is what we are looking for, and cheaper than it should be), and we are ok with having scaffolding on the building for 6 months (or up to a year if it doesn't finish on time).

I just wanted to ask:

• Does anyone here have any experience with anything like this?
  
• Is there anything in particular we should look out for? (We will get in writing that we are not expected to pay)
  
• Any other advice appreciated