Got a tow bar sorted for my M35 today...
Rated at 500kg unbraked and 1500kg braked (didn't require much capacity, only wanted to be able to tow the Jet ski for summer ).
Cost NZ$720 from North Shore Towbars in Auckland, NZ (Sorry, wont help you Oz folks, but if anyone in Auckland needs / wants one, go see these guys).
Thankfully they managed to accommodate the after-market rear bumper (Impul kit) and only had to cut a piece out about 1" x 2" right underneath so you can't even see it anyway and also had the tongue come underneath it rather than through it.
Anyway, some snaps for those who are interested to see the setup:
(Excuse the dirty car, needs a wash and the photos aren't the best quality but happy to take better ones when the weather fines up...)