I'm going private, but I had a scan at 8 weeks because I had some light bleeding (referred by GP), then saw the OB at 12 weeks and he did a quick measurement scan, but I didn't have the NT scan done. I've just recently had a 19 week scan. I think that's it for official scans for me. OB will be doing mini ultrasounds each visit tho (and I mean mini! about 1 minute.. if that)

My understanding is the 18/19 week scan is the important one, they check everything there, the brain, the heart, all sorts of measurements etc.