Finny,
This sounds like so many other stories others on the forum have experioenced - "Sorry, can't fit 2nd external gas bayonet due to changed regulations"
Do a search - you will find the threads.
Suggest you call Jayco and have them provide you with the regulation that has changed or call the appropriate gov. dept. that can confirm this regulation. Otherwise, press your dealer to have the 2nd gas bayonet fitted whether as a result of Jayco not fitting it o forgetting to fit it at the factory and feeding you this line.
We got our 17.56-2 delivered at end of Aug 2012 and on pre-delivery inspection I noticed only 1 or 2 bayonets fitted. Dealer noted it and had the 2nd one fitted as per contract - no questions and no excuses.
Yes we live in Vic, but I would suggest that Jayco quite often only fit one whe you are ordered and the provide the standard reason of "changed regulations".
Others in Vic, NSW and Qld have all been fed this line, but neither Jayco or dealers appear to have provided any documentation of the changed regulation/s.
We have used both bayonets - great to have them fitted at each end of the van as it provides great options for placing the BBQ on windy days.
Good Luck,
Rohan