He thought some sort of earth screen... maybe the last owners were paid up members of the tin foil hat brigade and went one further to have a faraday cage built above them :)
But as soon as i saw them i recognised them as electric heat mats, as i have some reptile heating mats i use for injured birds i look after, black tightly woven resistance mat with sewn on copper strips each side, placed inside a polythene type bag, the edges of the poly bag are trapped between the celing joists and the plasterboard celings, so it was put in as the house was built it seems,
They no longer work, a lot of them have had the connector at the ends ripped off taking part of the copper strip with them, and others have the cable cut (a black outer, green inner and single stranded cable inside that, terminating in a push on metal clip that is pushed onto the copper strip of the mats, then tape put around the connector end)
No signs of any controller, but i imagine there may have been a frost stat in the roof space to control them?
Am i right in thinking it was a way to keep the attic slightly warm to stop pipes freezing and/or condensation forming? probably used in place of traditional insulation? The loft space is just the usual storage area, and i don't think over ceiling heating is that good an idea... but there may well have been a cowboy selling it in the 70's :)
I can only imagine the bungalow was built at the time nuclear powered electricity too cheap to meter was on the cards, Wonder what the police choppers doing thermal scans for drugs farms in attics would make of the heat mats being on.