To keep the pesky invaders out:
Reduce the entrance size of the hive, probably opened fully during the recent hot weather, to give the bees a smaller area to defend,
Put out wasp traps, these can be bought or easily made with a jam jar with a hole made in the lid or from a plastic drinks bottle as shown. Bait with your favourite mixture or vinegar, sugar and salt attracts wasps but not bees. Do not use honey in the bait of course.