Bumble bees - buff-tailed? - and nest?

Bumble bees - buff-tailed? - and nest?

Observation - Bumble bees - buff-tailed? - and nest? - UK and Ireland. Description: Puzzled by this bees' nest(?). Seems a very odd place - out in the open on bare ground. Bits of wood shreddings and what looks like torn-up polythene along with other fibres. About 5 bees seen in total. In/on the nest, a bee about twice the size of th

Puzzled by this bees' nest(?). Seems a very odd place - out in the open on bare ground. Bits of wood shreddings and what looks like torn-up polythene along with other fibres. About 5 bees seen in total. In/on the nest, a bee about twice the size of the others. Also some little crater-like structures which seem to contain liquid, and some largeish (~5mm diameter) yellow-gold spherical objects. Would be grateful if anyone can explain what I'm seeing. Thanks!