This side has now been primed. Across the arms of the cross I intend to have a stretch of water. This has been tricky to model, but I am feeling better about it just now. My plan is to colour this with interference paints, which change their tone / colour when seen from different angles and in changing light.

Above: Some close-up shots showing details of the surface. At the right-hand end, is a section with broken mirror and CD bits. This section will be fixed into the open doorway, and should hopefully reflect light outwards. I may cut a 'window' into the doorway, in order to aid this.
The next stage is to colour both sides. Initially, this will be done with gold spray paints, but other colours will be applied by hand afterwards. The various elements will be attached after that process has been carried out.