I'll with hold my judgement there Peaky 
However 31 weeks is the next visit scheduled, dependent on your local Trust.
It goes something like this...
Booking visit, 12 week scan, 16 week midwife appointment, 20 week scan, 25 week midwife appointment, 28 week midwife appointment, 31 week midwife appointment, 34 week midwife appointment, then 2 weekly visits.
However, each Trust have different guidelines, and NICE guidance mean that the 25 and 31 week visit are only recommended for first time mothers. Which I think is tosh. Women need reassurance! Being seen at 16, then 28, then 34 weeks just seems awful to me.
Oh, and if you are 'high risk' you may be seen more frequently, or be seen in antenatal clinic as opposed to community.
The whole point anyway is that it is supposed to be individualised care. For example, you might see a woman at 34 weeks, and her BP has risen a little, but not enough for you to think sending her to the hospital is a good idea. So you might suggest she makes an appointment with you for the next week. Or do a home visit the next day to check your BP again. Professional judgements ;)