Is this a nest and which wasp species?
Looks like this is a European wool carder bee (Anthidium manicatum)
More precisely a female, judging by the round end of the abdomen.

Information regarding the nest it was found in:

These bees construct their nests in preexisting cavities, using the trichomes of wooly plants.
Females use their mandibles, which are sharply toothed, to remove trichomes from the stems and leaves of various plants. They then roll up the trichomes into a ball and bring them to a preexisting cavity. Inside the cavity, the bees fashion the trichome ball into cells, where they deposit an egg as well as a provisioning mass consisting of nectar and pollen. Once finished, she seals the entrance to the cavity with a terminal plug, which consists of inorganic and organic materials that she brings to the nest. Source