  We present long-wavelength neutron diffraction data measured on both single
crystal and polycrystalline samples of the skyrmion host material
Cu$_{2}$OSeO$_{3}$. We observe magnetic satellites around the $(0\bar{1}1)$
diffraction peak not accessible to other techniques, and distinguish helical
from conical spin textures in reciprocal space. We confirm successive
transitions from helical to conical to field polarised ordered spin textures as
the external magnetic field is increased. The formation of a skyrmion lattice
with propagation vectors perpendicular to the field direction is observed in a
region of the field-temperature phase diagram that is consistent with previous
reports. Our measurements show that not only the field-polarised phase but also
the helical ground state are made up of ferrimagnetic clusters instead of
individual spins. These clusters are distorted Cu tetrahedra, where the spin on
one Cu ion is anti-aligned with the spin on the three other Cu ions.
