Advice
How quickly can portable air conditioning cool a room?
What realistically affects how fast a portable air conditioner brings a UK room down to temperature.
What affects the speed
Room volume, insulation, glazing, sunlight, how much heat the building has already absorbed, and how well the space is sealed all change how quickly a room cools.
A correctly sized unit in a closed, shaded room will make a noticeable difference far faster than the same unit in an open-plan space with doors open and sun on the glass.
Getting the best from a unit
Close internal doors, draw blinds on sun-facing windows, seal the window kit properly, and run the unit ahead of the hottest part of the day rather than reacting to it.