I would probably be able to book it myself if I had the request from the midwife, but I didn't!
Bloodwork is easy here, they give you a little slip/note at the doctor's (like a prescription I guess) and you just walk in, sit and wait, give them the piece of paper and they do it for you!
Wish it was that easy for the U/S, but then again I'd still have to wait to see my midwife which isn't until next week!