Looks like a great track plan Mark and I totally understand the issue with moving house. Blockwall Junction is currently in bits and I don't know if it will be allowed to resurface once we've moved...
As far as the MERG kits are concerned, I'm assuming that you've got the following setup:
JMRI -> CANUSB -> CANCMD -> Track
At what point in the chain does communication stop? If it's between the CANCMD and the track, make sure you have the CANCMD in the correct configuration (one of the jumpers sets for programming track or programming on the main) and that you can connecting to the track using the correct terminals (again, one set is for a programming track or small layout, the other set is for use with a DCC Booster station).
If it's between the CANUSB and the CANCMD, check the wiring and the terminating resistors are in place - even if you only have the basic setup above, you still need the resistors.
If it's between JMRI and the CANUSB, which operating system are you using? The JMRI and Merg email groups are a very friendly bunch and you can ask almost anything on the list!
Kind regards,
Matt