John – I have a space of 6′ 2″, so it will be quite a tight fit but might be workable.
Nick – Yes, the helix would be located outside of the main train room. I have been looking at vertical plane solutions and the electrically operated lifts for raising TV’s might do the trick. They are able to handle the weight, the extendable reach is sufficient and adjustable, and the speed looks appropriate. So, I will do a bit more research on that solution.
Thanks for your replies.