I live in the roofspace of this house, and with the wonderful insulation, during the winter when it gets cold, it stays cold, and during the summer when it gets warm it stays warm
Having the velux windows doesn't help matters, and last year I ended up getting the outside pulldown blinds, as well as foil backed blackout blinds, including a nice airforce a/c unit from b&q - while the temp in the back garden was 30 this morning, it was quite comfy at 18 inside
The thing though is once it's down to temp, it's fine, but if you open the windows, it takes the a/c unit an age to drop the temp down again to around 25. I think the hottest it's been in here was 40 the year before last, I lost 2 hard drives that day too.
I shall find out what high temp we reached over the past few days when I get back to work - there's a met office reporting station behind one of our buildings at work.