If you are thinking buying in quantity of more than one, it might help to find a definitive copy of the Standard that applies in Australia and send it to Steam Traction World for comment.
They would be well placed to say if their boilers comply. They could also identify any place they do not comply and suggest options for resolving the difficulty. They would be more likely to help on a multi-item order than a one-off.
The other option is to obtain a copy of BS2790 and send it to the relevant authority in Australia so that they might comment on if it is an acceptable alternative to the local standard or again identify specific items that need further attention.
If I put BS2790 into Google, the second link I see is a pdf copy of the standard, so you could do a 'compare and contrast' yourself in advance of any further action (i.e. the lawyer version where you do not ask any question to which you do not already know the answer).