Plasterer also booked

We were recommended a plasterer about a year ago - and we had a chat with him to let him know we were thinking of using him - about 5 months ago. He has agreed to do the job - but only the plastering - not the plasterboard (or slabbing) on the ceilings or inthe upstairs at roof level. Inside and out and the outside of the garage will take him about 5 weeeks. He could start the outside as soon as the windows are fitted - but he might want to do inside first? I still need to have a chat with him when we know when the elctrician and plumbing first fixes will be done.