Short version: MakerSlide will be delivered to us between 16 and 20 November.
Long version: I’ve been a bit naïve. When I talked to our current supplier of MakerSlide, before I committed to them, they told me that, if they had uncut rail in stock, the turnaround time for an order would be 1–2 weeks. Now I’m told it’s actually 4–6 weeks, and it’s always been that. They were also similarly optimistic about the time it takes to extrude it (2–3 weeks — in reality 6-8 weeks, occasionally more).