Competent Air Con in SE Melbourne

Side comment; ReGassing is not a full service that gets the system working at its peak (this is what most air con shops will offer).
Spend some simple spanner time can save costs, if your system is de-gassed, easy to clean evaporator (warm water and plain dishwashing liquid) and replace your tx valve (under $100 from supercheap). Can be done by undoing four bolts nuts under dash and two lines joints under .
Lots of online guides.
With the age of the mr2 air con, it makes a great performance difference in doing the above, for longevity replace the o rings, and dehumidifier (when air con guy re-gassing).

If all that has been serviced in the timeframe listed, you should only require gas. For that any monkey with gas (with die) can do.
Air con lasts differently depending on how “full” they put the gas in, how much it’s used, and any issues (hence the die just so it’s easy to check over for any leaks).
Hopefully a few Melbourne owners can chime in as to where they go...

Although people probably know this, from what I have been told, it's important that the A/C should be run from time to time, even in mid winter. 
Something about maintaining seals?