FeSe1-xSx is an important model system for investigating the relationship between superconductivity and nematicity. The nematicity can be suppressed systematically by the isovalent sulphur substitution which vanishes completely at x = 0.17. Here, we propose to expand our previous work on single crystals of FeSe by studying single crystal samples of FeSe1-xSx (x = 0, 0.1, 0.17, 0.2, 0.25) and investigate the evolution of the superconducting gap structure as a function of sulphur doping x, namely the strength of nematicity. We also propose to investigate magnetic instabilities which arise in the nematic state and observe their evolution in FeSe1-xSx (x = 0, 0.1, 0.17, 0.2, 0.25) as a function of sulphur doping from the zero-field µSR measurements. We ask for 13 days of MUSR beamtime with 3He and 4He cryostats to complete this proposal.