Debris discs around main sequence stars are belts of planetesimals -- asteroids and comets -- formed in the protoplanetary discs around young stars. Planetesimals comprise both the building blocks of planets around young stars and the source of dusty debris around older stars. Imaging observations of dust thermal emission and scattered light reveals the location of these planetesimal belts around their host stars. Analysis of debris discs observed at millimetre wavelengths revealed a trend between the disc radii and the host star luminosities. We previously performed a homogeneous analysis of debris discs resolved at far-infrared wavelengths by Herschel, fitting the distribution of radii as a function of stellar luminosity. Here we present an extended sample of spatially resolved systems, analysing their dust properties, i.e. minimum grain size, slope of the size distribution, and total mass, using a parametric model. We apply a variety of dust compositions including mixtures of amorphous and crystalline silicates, carbonaceous species, and water ice to identify the range of properties consistent with the observed emission.