I have gone ahead an ordered a ASI1600MM-Cooled from Bintel. I am told by John that they expect the first shipment from ZWO at the end of this week (today?), and that they hold enough pre-orders to pretty much run out the initial delivery.
Now I am looking for a 36mm filter wheel that suits (as I already have a set of 36mm narrow band filters and I don't wish to sell them). The Starlight Express wheel looks promising.