Advice for keeping cool. Air conditioning unit or fan?

If your buying from btrand new I suggest an extractor fan.
This can serve several purposes,as it can remove pollen spores from your home as well as covid 19 spores.
Just make sure its getting evicted from your home via the windows.

Ours are still in the loft but don’t think they are Dyson. One came from Aldi/Lidl. We put the timer on so it starts quite early before it gets hot. On very hot days position a frozen cooler bag block in front of the fan so it blows out really cold air. It kept me sane when I was going through chemo style treatment in a heat wave.

My daughter has one, it is brilliant, the best cooling device I have come across.