CDFs of the fraction of BNS mergers within the observed offset F for the fiducial model. Top row: Models where the stellar component is a disc. Bottom row: Models with a spheroid. Left column: Hosts with a Sérsic fit. Central column: Hosts with a Sérsic fit but modelled with the mass-size relation. Right column: All the hosts modelled with the mass-size relation. The shaded areas indicate the uncertainty due to the astrometric error on the observed offset, while the dotted lines indicate the uncertainty due to the spread of the mass-size relation. The host types are shown in the legends.