I picked up something like this about three years ago. No regrets.
Though I can't help but feel like I'm also adding to the climate problem.
The hard bit is our walls are solid with no space for ducting of any kind
I'm planning on ducting through an existing window vent (or two) 
Have just acquired a 6" duct fan that can move up to 402cfm, so hoping I can tap into some of the cooler evening air to help with night time sleeping, without going to full-on aircon at this stage.
Although, I suspect that the solid walls / roof space act as a storage heaters to some extent.
This is how I see the UK normally, outside of cities... just a lot less blue sky :D 
These will sort of fit UK style casement windows:
Had been thinking of doing something similar but with a better fixing arrangement.
