Originally Posted by Mr.Manchester

I used to be a pest control tech for a living (now im a pest control tech on here, how ironic )

Have a look outside and see if theres any holes in the pointing between the brickwork, also as Al Bags said have a wander in the loft for a look.

Im sure you can buy a strong spray from B&Q these days, if theres a nest in the loft then one trick is to take a flash light, and shine it on the nest, then get the spray and spray into the beam of light so as the wasps fly towards the torch they get covered in the stuff, the chemical i used to use was that strong they used to instantyl drop to the floor

But at this time of year they will all be dead soon anyway