I can't help you with the timelines up there I'm afraid, but you could ring the receptionist & ask if they've sent one or when they are planning to?
My mail is rubbish down here & I actually never received 2 appointment letters I should have, so if I wasn't periodically ringing to make sure they hadn't forgotten me, I would never have known!
The first time, I found out in time to actually attend the allotted appointment but the second time I had to arrange a new appointment, after a long argument with the snotty woman on the other end! She initally refused & told me they strike non-attendees off their list, but I argued how could I possibly attend if I never received the sodding letter???!!!! I was actually really annoyed as it was for my sleep apnoe test & it was the last thing I was waiting for. I luckliy managed to get a cancellation only a couple of weeks after the orignial appt, but it could set some peopl back weeks depending on their area. Sorry, bit rambling there wasn't I?!