We perform a likelihood analysis of the constraints from accelerator experiments and astrophysical observations on supersymmetric (SUSY) models with SU(5) boundary conditions on soft SUSY-breaking parameters at the GUT scale. The parameter space of the models studied has seven parameters: a universal gaugino mass m1 / 2, distinct masses for the scalar partners of matter fermions in five- and ten-dimensional representations of SU(5), m5 and m10, and for the 5 and 5¯ Higgs representations mHu and mHd, a universal trilinear soft SUSY-breaking parameter A0, and the ratio of Higgs vevs tan β. In addition to previous constraints from direct sparticle searches, low-energy and flavour observables, we incorporate constraints based on preliminary results from 13 TeV LHC searches for jets + [InlineEquation not available: see fulltext.] events and long-lived particles, as well as the latest PandaX-II and LUX searches for direct Dark Matter detection. In addition to previously identified mechanisms for bringing the supersymmetric relic density into the range allowed by cosmology, we identify a novel u~R/c~R-χ~10 coannihilation mechanism that appears in the supersymmetric SU(5) GUT model and discuss the role of ν~ τ coannihilation. We find complementarity between the prospects for direct Dark Matter detection and SUSY searches at the LHC.