I’m new to this forum, I noticed that someone had asked about spray painting.  I am a spray painter. In other countries spray painting walls and ceilings is very common but, as yet not in the Uk.  It is better, a lot faster and usually works out significantly cheaper.  Defying the “House Builders Bibles” theory of the triangle.  A typical three bed semi can be prepared and painted with two coats in one 8 hour day by one person.   It does have restrictions, best on new plaster