I’ve had this running for 3 days now and so far so good, it’s been around 30 degrees outside and it’s keeping my room (18ft x15ft) comfortable in the day, at night it is lovely and cool, I can sleep well! 
As mention it only comes with and exhaust attachment for sliding windows, not casement but I bought an “apron kit” online for £12 which has solved the issue well. 
I am considering buying the larger BTU version for my living room. 
All in all this has been an excellent purchase.