In Vic I recommend these guys-
http://www.precisionplating.com.au/

Cost? After doing a lot of comparison shopping I have found that you get what you pay for. A cheap chrome plater will give basic results, whereas spend a little bit more and you will get a high polished showroom finish.

Most will do prep work and removal of surface rust/paint etc, but keep in mind the more time that needs to be spent by them in prep work, the more this will add to the overall cost. So if you want to keep costs down, do as much prior prep work yourself as practicable.

The plating itself is not the costly part, but the labour involved in polishing the chrome work to a mirror like finish.

This was a standard black Bally/Williams coin door before chroming done by a plating place in SA: