We report a magneto-optical study of record quality MBE grown On,Ga)As/GaAs samples taking into account the Coulomb well (CW) potential and strain effects. A rich fine structure of heavy and light hole magneto-excitons was observed. Additional hole confinement due to its Coulomb attraction to the electron localized in a quantum well (QW) appears to be of key importance for light-hole excitons in (In,Ga)As/ GaAs QWs. The CW depth for light holes was directly experimentally estimated. Heavy hole masses, m(hh), in the first quantum-size subband of the InxGa1-xAs/GaAs heterostructure were estimated also. Results agree with theoretically calculated heavy hole mass taking into account deformation of the InGaAs layer and tunneling of light holes.