We present a refined version of our three-generation flipped ,SU(5)×U(1) string model with the following properties. -The complete massless spectrum is derived and shown to be free of all gauge and mixed anomalies apart from a single anomalous U(1). -The imaginary part of the dilaton supermultiplet is eaten by the anomalous U(1) gauge boson, and the corresponding D-term is cancelled by large VEVs for singlet fields that break surplus U(1) gauge factors, leaving a supersymmetric vacuum with an SU(5)×U(1) visible gauge group and an SO(10)×SO(6) hidden gauge group. -There are sufficient Higgs multiplets to break the visible gauge symmetry down to the standard model in an essentially unique way. -All trilinear superpotential couplings have been calculated and there are in particular some giving mt,mb, mτ≠0. -A renormalization group analysis shows that mt<190 GeV and mb≅3mτ. -Light Higgs doublets are split automatically from heavy Higgs triplets, leaving no residual dimension-five operators for baryon decay, and the baryon lifetime τB ∼ 2×1034±2 yr. -There are no tree-level flavour-changing neutral currents, but μ→eγ may occur at a detectable level: B(μ→eγ) ∼ 10−11 −10−14.