As others have recommended I've got an old (10 years+ ?) portable aircon unit. I use it very occasionally in my little office as when we have temps like yesterday as it becomes unbearable with all the computer monitors acting like heaters. At such times it can be a godsend. You might want to think about one - they're not that expensive, from about £250 upwards (last time I looked), depending on features and how quiet you want it to be. It might be worth looking at a few in a shop as you might want to judge the weight (mine is heavy and the weight distribution is odd) and hose length practicality etc etc.