Had booking appointment at 12 weeks, then 16 weeks (for bloods, not just triple test but full blood count, blood type, glucose levels, HIV, Syphillus (sp), hepB, anaemia and urine for abnormal bacteria) and 24 weeks. 28 (at hospital as I need antiD), 31, 34, 36, 38 and 40 to come. I had the impression that the blood tests just have to be after 14 weeks and no end time so I guess they will do them at 22 weeks.
I have to say waiting for initial 12 week appointment was the worst but I feel it's all too long when you worry about it all. Now I'm feeling the baby moving (from 17 weeks) I'm not so worried and there really isn't a lot they can do for you. 16 wks til 24 wks was a long time too but I just have to keep thinking it's good that they don't want to see me as there's nothing to be concerned about!
To reassure yourself come on here, ask questions and read as much as you feel is good for you. There's a lot of positive things out there as well as the horror stories and it really helped me feel in control.
Things do differ between me and a friend who's baby's due 10 days after mine and we are in neighbouring counties so I wouldn't worry too much about what other people are getting just what you feel happy with. As others have said you can make an appointment with doctor if you feel uneasy.
Good luck and congratulations on your scan!