Looks like a nice route. I may be tempted.
For the chap who asked, the chairs on the current sleeper don't recline and its quite difficult to get to sleep in them. That said, the sleeper trains are being upgraded at some point in 2018/19 and so this might (or might not) improve by the time of the event.
Sometimes the easiest option is to box up the bike and fly to Edinburgh, if there is the facility for left luggage at the Arrivee, particularly if you can find someone's sofa to crash on (I'm lucky enough to have family up there).