I've fermented with Nottingham dry yeast and Wyeast 1056 up to 82F with no ill effects. There were definitely some more noticable fruity esters, but it wasn't excessive. The other thing you can do to keep temps down is to get a big tub and fill it with cold water from the tap, and place your fermenter in it. Add ice or frozen water bottles to the tub to keep the fermentation temp down. Once the krausen has fallen, just let the temp go. Cheers!