After cancelling the order, and finally being given the offer of an October refund, compensated hashing, or hosted hashing, I decided to negotiate on the amount of hashing I'd receive in compensation.
I'm happy to say that within 10 days of concluding those negotiations, my Coincraft Desk units have arrived from Bitmine.ch, and are now up and working (after a little bit of maintenance caused by one of the Pi controller boards coming loose).
Its doubtful that I'll ever manage to quite breakeven now (unless the exchange rate goes silly), but the risk of waiting to see whether I'd see any sign of the refund was too great.
I've learnt my lesson though... next time I'll hire an engineer to do the ASIC design and build the units myself!
I'm just glad to be able to draw my particular case to a close.
Hope the rest of you in limbo manage to sort things out one way or another.