Up until the last decade or so, hot summers have basically been associated with a blocked situation with depressions stuck in mid Atlantic, so some good surf, not rough seas, just a decent long period clean swell. It seems that is no longer the case, there's been nothing much happening in mid Atlantic.
To demonstrate this this graph has just appeared on MagicSeaweed
The mean Summer temperature anomaly is from Camborne, the Summer wave height anomaly from Fistral, Newquay.
So depressions clearly aren't getting stuck in mid Atlantic, it would appear there is a split going on, with depressions tracking, generally further north than normal. A split in the jet stream perhaps, down to less ice in the Arctic?