Hi Rob and Fishman,
All of the decoders were set for DC and DCC so I have changed all to DCC only. I have had the locos sitting on the layout with power on and so far no movements.
I like the idea of checking with Hornby about having the firmware but being 12,000 miles away is a problem but I will contact them to see what they say.
PS Fishman, where in Oz are you? I am in Hastings, Vic