Hi, I ended up going through lgnz marketing folks via their Facebook page, they gave me a link to get the 55 download. I know the AU & NZ firmware has differences so no point sharing that but I'd suggest try through Facebook because you're right their sales support people are as useless as tits on a bull...
But if you want to risk it this is what they sent me, it has solved all the problems pre 55 I was also experiencing...
Here is the download link, you will need to place this file in a folder LG_DTV on a usb stick, and insert to the TV while left on an input.
Let us know how you get on.
http://we.tl/68nPCitT8T