My recollection is that Royal Mail was the cheapest way to post to Australia for parcels weighing up to 2kg after which we used to get quotes from a company such as Transglobal - see https://www.transglobalexpress.co.uk/?gclid=CjwKEAjwgZrJBRDS38GH1Kv_vGYSJAD8j4Df4M-IqiK9R9lXSTEZEkgRNqYwD0cXCyPPZgDPtLBIuRoCQS3w_wcB
Things may have changed since Steve and Lisa took over Totally TTRs and there may be better companies to use. Over to Steve on that one!
Definitely won't be using parcel monkey, I only used them as a customer wanted to save a little money and just caused a lot of aggravation to everyone involved.
Send me an email sales@totallyttrs.com and I can give you a quote.