A series of modelling tools have been developed for fractured media, where the problem of connectivity is the major mechanism governing flow, and mass or heat transport. These are boolean models, where randomly distributed fractures are generated in space. Flow and transport properties are then distributed at a local scale for calculating global hydraulic and dispersive behaviour. Ensembles of realisations are generally generated, but are difficult to condition on measurements. Based on the experimental results obtained at great depth (c. 2.5km) at the Rosemanowes HDR site (Cornwall, UK), this approach is shown to be appropriate for most of the available data. These data are integrated in a single model and used to produce relevant estimates for the main hydraulic parameters. Flow through stimulated fracture networks is then investigated and the thermal behaviour of the simulated geothermal loops is derived. The discussion focuses on thermal drawdown with elapsed time and demonstrates the high probability of having preferential flow connections (short circuits) between the boreholes.