Get off to B and Q and get a container of ANT POWDER. It has Permethrin in it, same as council stuff.
Do it in the LATE EVENING when they're not flying.
Puff it around the area the wasps are coming in/out from. (They pick it up on their bodies and transfer it around the nest). You can't puff the container upwards, as we found out, so maybe work out a way of tipping it from another container if need be. This is serious stuff...... COVER YOURSELF UP AND DO NOT INHALE!