There is some kind of insect trap that the wasps will fly into to feed on and then they can't get out. I'm sorry but I don't actually know what one is called.
You can buy 'Wasp Nest Killer' from a garden centre. Its a powder and as long as you can see the entrance to the nest, give it a good puff round the entrance. The wasps get it on themselves and take it inside, which will kill them off. Problem is, it makes em pretty angry, so if you are up a ladder beware and get ready to make a hasty descent! Cover your arms etc, face if poss or at very least wear safety glasses. Have fun!!
Use a powder as Landscaper suggests. I've had good results in the past with this one. Should be available in any garden centre. Squirt the powder where the wasps will walk over it and carry it on their feet into the nest. I haven't had any trouble applying it - the wasps were more curious than angry!
When I was a child, I used to love killing wasps. I used to burn them I hope you do not work for RSPCA. Once I got stung by 13 (which I could count). After that whenever I got stung, poor wasp died soon after. But do not act upon my advice and do what landscaper is suggesting. And yes do cover yourself. Good luck
Keyplus 90 - if whatever stung you died soon after it wasn't a wasp it was a bee. Please don't kill bees, there is a serious shortage of them due to hive collapse and without bees we will be in serious trouble