Looked in on the new swarm today. The good news is that they have settled into their new home, rather than simply buggered off.
These new bees are *very* busy, and *very* aggressive. The slightest shake or knock, and a great swirl of bees pours up at me! Right now, they are building up the comb in the brood box, and already storing honey and pollen in half-built cells.
The first brood will be due to emerge in 24 days. I will check again on or around 12 June, which allows a few extra days for the comb to be completed.
By the look of them, these are Carnolian rather than black bees.