I sympathise - my DD has never been the best sleeper, but from 14 to 18 months she was probably just waking up once to get her dummy back.
As soon as she turned 18 mths, oh dear ... She stands up in her cot, wide awake, wanting to get up. It can be 1, 2, 3 am - but always in the middle of the night ...
She's nearly 20 mths now and very slowly it is getting a little bit better - shes sleeping through one night then up the next, but perhaps only for an hour. Its coincided with total explosion in speech (I mean explosion - at 17 mths she had a few words and understood a few things, now she has hundreds of words, speaks in little sentences and understands pretty much any simple instruction you like).
She's started doing imaginitive play, looking after her "babby", running off down the lane exploring etc etc - its really like she has gone from baby to child in a month.
Fingers crossed she is coming out the other side of the 18-21 mth regression now!!
On the plus side, she is much more fun to be with now during the day, and I have tried to help her sleeping by making sure she gets up at a good time and gets lots of fresh air and stimulation.