Scanning near-field and time-resolved photoluminescence spectroscopy have been applied to characterize single m-plane InGaN QW structures. The PL spectra were found to be formed by emission from the extended and the localized states. Lateral dimensions of uniform potential regions were placed around a few tens of nm. It was shown that optimization of the template for the QW growth results in a more uniform emission spectrum and a reduced effect of carrier localization. The radiative recombination time at low temperatures was found to be short, about 0.5 ns. At room temperature, nonradiative recombination via efficient recombination centres was prevailing. Complexes of Ga vacancies with O were suggested to play this role.