I had to make the appointment myself. Went to see the GP and he was useless, just told me to keep taking folic acid and make an appointment to see the midwife. The receptionists did tell me though that the midwife doesn't like to see anyone before they are 10 weeks, so they should be in touch soon if that's what happens in your area. If you don't hear from anyone I'd give your GP practice a ring and ask them, otherwise you should be able to contact your local Primary Care Trust (details on the NHS website as to who your PCT is and how to contact them) and they should be able to advise you on what happens in your area and how to contact your local community midwife team.