Thanks to all of you for pointing me towards a wealth of information. I now have a lot of reading to do and will no doubt be posting further questions as they arrive.
I model British outline in P4 and although this will remain my main interest, I would like to model an Australian prototype. I have lived here in NSW for almost 30 years so it's about time and retirement provides an opportunity.
A few years ago I visited Tocumwal and was intrigued to learn about the broad/standard gauge interchange and think it would make an excellent subject for modelling with a mix of HO and EM gauge track and set in wartime or the immediate post-war period. There is obviously a lot of research I need to do, not just for Tocumwal but to understand the historical and operational context.
Thanks for helping me to make a start.
Adrian