We are not modelling anything specific. We haven't picked a single era, epoch, country, region or other archetype to go by. What we are building is a fantasy layout, on which it is entirely possible that locos and rolling stock will be mingling which never would have had any geographical or temporal proximity in reality.
When we decided to go H0 scale, one of the drivers had been the fact that local model manufacturer Southern Rail Models had announced a model of the Queensland Rail 2300 Class diesel locomotive. Since I see these regularly close to where we live, it made sense to get one of those for our endeavours.
With the track plan decided upon, and the layout making progress, there was somewhat of a need to test the work being done. I had previously bought a cheap(ish) loco to do exactly that, but it turned out to be DOA, with the shop having no suitable replacement.
A few weeks back, after understanding the difference between H0 and 00 gauge, I decided to switch to H0, simply because it offers a much larger variety and is not just limited to primarily British models. I sold my 00 locos and rolling stock, and pre-ordered a H0 scale Queensland Rail 2300 Class diesel loco to start off the new fleet. The reason for this pick is that we live close to the West Moreton system, on which the 2300 is the primary freight workhorse.