PROBLEM SOLVED. Power supply connector into fusebox has suffered a meltdown of the connector supplying lighting.. Red lead to the brown connector on the fuse box arcing and burnt away. Virtually the same problem as on the Phase 1, circuit exceeding the rating of the connector.
I have Renault Espace 2.0L petrol 8 valve late Phase II/early Phase III. Last weekend all the lights failed while out. They were working, we stopped and unloaded and went to come home and there were no lights. No side/tail lights, no headlights, dipped or main beam, no lights indicator or main beam indication on the instrument panel and no panel lighting and no horn. Checked the fuses (Phase III fuse box in top of glove compartment) and the fuses in the engine bay. All appear to be OK. Changed steering column switch with no change other than the horn worked (and the radio started working after many months, coincidence I think). There appeared to be a 12 volt supply to the switch but this goes to zero when the switch is moved to any on position so probably a back feed from another circuit. The circuit diagram shows that everything is fed from a 12 volt always on accessory plate but no indication of where it is and whether there is a main fuse to that plate. In addition to the fuse box there are a number of relays and fuses above the fuse box and under the fascia but they are difficult to get to but appear OK.