It's not 'too' difficult.
You need to have owned and used the car in the UK continuously for at least 12 months.
You need to seek prior approval from the Australian Federal govt before booking shipping.
Modified cars generally are not allowed - i.e. no mr2 v6 conversions.
Like DTM asks, emigrating, returning citizen or otherwise? If you want to send it to a buyer here - it won't happen.
You can do it under the 'personal import scheme' if it's your personal import only.