Buzz, buzz, buzz!!

Yep

Oh dear, sounds like you might have to contact a pest control company.?

Can you just open the door a little bit and puff the powder in?

DO NOT OPEN THAT DOOR just in case. Wasps are very good at communicating when they are hurt I believe, and will rally the troops to retaliate. Also, it could be Bees as we had this problem many years ago.
Get a Pest controller MiniMoon
ASAP.
Keep us posted.

Could be bees. We had a bee swarm in our chimney when we moved. However no one could come until the next day and they had taken themselves off by then. I wonder if you go outside and look at the chimney you might see who is coming and going?

Yes we had them in the chimney, we lit the woodburner and had it going full pelt to smoke them out. Not had them back since and that was a couple of years ago.

Well, the buzzing stopped. I am wondering if the wasps were outside the chimney. I was alone in the house and everything was quiet. We have a pear tree opposite the house that has been alive with them recently, attracted by the aphids on the leaves.
If I hear any more buzzing I'll let you know.

If it is bees then, apparently they are unlikely to return next year. My mum had them in her roof last year and they have gone. I contacted the bee keepers association for advice.