There are of course various choices for connecting up a plumbing system. Obvious choices are brazing, press fittings, brass compression fittings using copper olive inserts, or the more old fashioned brass flared compression fittings.
The cheapest approach is to use flared copper compression fittings, and these can often serve in place of barrel unions to allow pipe sections to be removed for maintenance.
It is possible to use Kempress press fittings fittings from Plumbingsales.com.au and cheaper than the B-Press fittings available from Reece (even at trade rates). Appropriate press tools such as the Rothenberger 4000 B-Press Tool kit can be hired from Reece (Torquay) for $100 a day, or an equivalent from Kennards (Geelong) for a little less. The Kempress fittings are universally able to be fixed with any of the major available press tools. They are however more vulnerable to heat because of their inner silicon sealing olive. Fire rated fittings are available but at an considerably more elevated price.
Ultimately, for reasons of availability, flame resilience, and cost (but not necessarily ease of construction), flared fittings were used in most situations, with an occasional use of a copper olive insert compression fitting where it was cost effective and appropriate. Where DN50 copper pipe was utilised, the ends were annealed using a MAP gas torch prior to flaring with a flaring block and pin.