Posted: 30/08/2013 at 11:39
I have the same problem in my garden near Cambridge. I suspect some form of aphid on the bay leaves but there are no obvious visible signs.
In the past I have used the vacuum cleaner techniqe to remove the wasps, wirh a squirt of insecticide into the suction hose every so often. This makes sure that the wasps are killed and don't fly back out again when the vac is turned off!