Get some ant powder from your local supermarket for under £2.
In the evening when they are more docile, puff some at the entrance/exit points.
Any returning wasps will soon spread it inside and within a few hours they will all be dead.
Ant powder contains the same stuff that the councils etc use and is very effective.
When I used some on my chimney nest it was very funny listening to the ping, ping, ping as they fell down onto the back of the fire minutes later.
Then later you can get up there and sort out the old nest, then wash it all down for the birdies.
Spot on advice.