jilly, I posted an almost identical 'help' thread about a month ago, regarding my (nearly) 2.5 yr old dd2 who was up and yelling every night.
Things here are better, although not perfect.
I got loads of helpful advice and went with a combo of sleep book, reward chart and controlled crying (although it wasn't crying, more like just leaving her alone).
The sleep book I adapted and instead of having photos of her having tea, bath, story, kiss, bed asleep....I cut to the chase and had a photo of her asleep stored n the computer. After story time we went to the computer and I showed her the piccie and said how I wanted her to sleep at night NO CRYING.
She destroyed the star chart, so there was a treat promised if she didn't cry/shout/scream in the night.
We had a stair gate up in the doorway to her room.
When she woke up she got 1 visit (to check she hadn't done a poo...something she did with regularity). And then we left her.
First 2 weeks were bad...I won't go into details...I'll leave you to imagine it
Things are much better now. We occasionally get a night where (we think) she is sleeping through. Most nights she is still up, but doesn't always cry/scream, and settles herself back to sleep.
She spends a lot of the night on the floor (her choice), but I refuse to let myself get into a habit of returning her to bed several times a night. If she wants to get cold on the floor, that is her problem.
Sorry that was long. We've been where you are, but things here are getting better (hurrah).