Nests in my attic

[coteba5]

Can anyone identify what these are? :
I have found 2 grey/blue nests attached to the insulation between the rafters in my attic. Each is about the size of a golf ball and has a 10mm(about half inch) entry point at the bottom. The insides were empty. They look quite fragile.
I found them by chance following what sounded like a bird fluttering in the attic - no sign of a bird and no obvious access point for one either.
Answers most welome.
John

[LoftyLottie2]

Queen Wasps nest?

See the third paragraph on this link.

http://www.trapawasp.co.uk/about_wasps.htm