The cashback was paid very quickly, especially when considering this type of retailer. I believe I booked the tickets in early October and they have just paid - mid November. Brilliant.
More generally, I think the Caledonian Sleeper is a fantastic service with a great, easy website. Admittedly there are few occasions when I actually need to take the sleeper, but I relish it when the opportunity does arrive. Of note - standard class accommodation does not come with a booked dinner table seat in the bar - however (something that's not always clear depending on the steward) you can make use of the bar. Definitely the most romantic of ways to travel.