With the entire layout rotating, there was the problem of how to transfer power from the static baseboard to the revolving track.
The technical term for this sort of set-up is "slip rings". I call it a bodge job.
Looking for a cheapo way of doing this made me think of cake bases.
Phoning round local wedding party organisers drew a blank until one of them mentioned her supplier: a shop only a couple of miles away. I bought two 18" wedding cake bases, stuck masking tape around the edges and then copperfoil tape on top.
The cake bases were glued to the layout, and wires from the track were soldered - as delicately as I could manage - to the copperfoil tape. Power from the transformer goes to two sets of wipers on a post; these then wipe along the copperfoil tape et voilà! Le travail, c'est un bon un!