You could look for a second hand portable air-con unit I guess. I've seen new ones for a few hundred pounds before and I dare say you'd find a few on Ebay and the like. Bit of a risk buying second hand but they'd be a lot better and a lot less hassle than one of those 'cooler' thingies.
Something like this maybe:
http://www.ebay.co.uk/itm/Portable-A...item4ad856d6c4
They're a lot bigger though.