Chaps,
Many thanks for the comments and suggestions.
I had had thought long and hard about screwing in from the bottom, but using foam insulation as the baseboard and pvc foam board as the track base seem to preclude this - I have doubts about self tapping screws lasting beyond one removal of a coil, hence my thoughts about hanging them from above, which would also allow a bigger area for weight distribution. I completely agree about the importance of stopping the bolt spinning. I had been thinking about either using a lock nut between the coil and the track base, or a lot of expoy adhesive!
I confess I hadn’t thought of a tee nut, which is an excellent idea if I can force them home into the foam board. I shall experiment and report back!
Regards
Duncan