The series presents varied magnetic ordering behaviour within compounds that are structurally identical except for slight differences in lattice parameters. The compounds are quasi-two-dimensional and order at temperatures between 1.7 and 20 K. The two magnetic structures of have been refined and the results compared to a previously unpublished magnetic neutron diffraction study of most of the series. All four compounds in this study have been examined using zero-field and longitudinal-field . In and a systematic build-up of magnetic correlations occurs as the magnetic ordering temperature is approached, while in the Gd compound no increase of magnetic correlations is observed within the experimental resolution of 0.1 K. In , a linear increase is observed in a log - log diagram of the muon depolarization rate as the temperature is decreased from 30 times the ordering temperature towards . In three of the compounds ( and ), two distinct muon sites are observed. The exponents for the damping as a function of the reduced temperature are found to be dependent on the muon site, especially in where the signals from the two different sites can be best separated.