I understand that the reproduced, spiral-bound version of Dartington's book contains the detailed plans for several variants. See:
http://www.amazon.co.uk/New-Beekeeping-Long-Deep-Hive/dp/0905652517/ref=sr_1_1?ie=UTF8&s=books&qid=1252347627&sr=8-1
I also found a carpenter near High Wycombe...