Thank you so so much for your advice, I got the job!
For anyone else interested they also asked questions about what physics I knew regarding ultrasound and explain how an ultrasound image is created. Some scenario questions like what would you do if someone wanted to film an obstetrics scan, and what would you do if someone demanded you tell them the results after an abdominal scan. They asked about safety implications in ultrasound and what legislation I was aware of. Then some more question about what qualities I think a good sonographer should have, and what I thought the most challenging part of being a sonographer would be.