This process was not quite as easy as it sounded. There were quite a few worms left in the 'compost' and I ended up donning a thick pair of gardening gloves, 'sieving' through the compost with my hands and removing the worms to replace them back into the wormery.
I couldn't decide whether these were 'loser' worms who had never made it out of the bottom level, or 'champion worms with attitude' who headed to the upper levels for feasting and returned to the lower levels for a rest.
Anyway, rescued (recaptured?!) most of the worms and have put them back in the wormery. This process took about half an hour and I can't help thinking there must be a better way. Any other worm farmers out there with any suggestions?
It occurs to me that this is the first full cycle of the wormery. We started in January, so it has taken about 4-5 months to fill the wormery with scraps and get the first compost out. It will be interesting to see how long it takes now for a level to be ready for emptying.
Will now start to monitor (roughly!) how much waste is being consumed by our worms.....