Woohoo! This is something 99.9% of the world won’t care about, but I spent the whole morning trying to work out how to add backorder delivery options to the shop website. After beating my head repeatedly against a brick wall, I finally found this forum post which spells it all out in detail. So now I’m just linking it in the hopes the Google ranking will go up and the next poor sod won’t spend as much time looking for it as I did.