FYI - Thought this might help anyone renewing their contents insurance soon. Michelle Luscmbe has kindly checked the construction of the roof with Sweetings and asked me to post this on the building insurance page:
It is a suspended timber flat roof, originally covered with asphalt but more recently two thirds of the roof has been overlaid in a single ply system over the top of additional insulation. The other one third remains asphalt.
The mansard element of the roof is tiled but the main section is flat and as described.
*The single ply system is a pvc product that is mechanically fixed directly over the asphalt. The joints are heat welded and there are various edging details to weatherproof the perimeter