Cass I had the EXACT same thing happen to me here in Brissy.
I got a referral for a NT (nuchal translucency scan) and I booked an appt with QDI (Queensland Diagnostic Imaging). When I showed up for my scan, I was then told that they do not do them there, or at ANY QDI's anymore.
I was in tears with frustration, but luckily my GP was able to get an appt at the RBWH for a scan within the time frame .
I would go back to your GP and demand that they get you booked in for a scan on time! I'm fairly certain that any doctor should be able to refer you to a hospital for a scan....

All the best Cass... *hugs*