Advice wanted for buying a B+ by travelling Aussie.

Well, it won't fit the budget bill, but a decent 18' B+ with rear entry is made by Chinook. Not sure how they are doing these days (they've gone out of business several times, then been resurrected, over the years) and their RVs are relatively expensive. Nice little units. We had a used one for a while, back in the early 80s. There aren't many of them around so finding a used one isn't something you can count on.