Hiya becky have you looked at this thread
http://babywhispererforums.com/index.php?topic=46907.msg315343#msg315343 ? (hope that link works!)
In our case, on the first night, gave him a df, which I've never done before because he always would wake at 10/11 anyway. But i picked him up gently before he woke up and made him take as much as I could. Basically kept putting himback on, both sides until he was unresponsive. Than when he woke at 3 I gave him expressed milk. Every night I diluted it more and more until it was just water (over about 4 nights).
On the 5 night I dropped the df and he didn't wake up till 3. At this point I did pu/pd for 20mins. He cried but it was more of a moany cry than screaming. The following night he went back to sleep with just a shh/pat. On the the 7th night, he cried out and rolled over and wen back to sleep without my intervention. And the he sttn for a few nights.
It didn't stick unfortunately because all this extra night sleep meant that he now needs more A time and less naptime during the day, so we got EW, so I'm having to tweak his day routine. But he now sleeps 8/7 hours solid at night rather than 3/4. He's sick at the moment, but once he's better I'm gonna wean the 3am feed the same way again.
I think it says on the above link, that night hunger becomes a habit, so you have to retrain their bellies. I know my lo would feed all night and then not take a proper morning feed and refuse breakfast. Now he has a solid feed some where between 5 and 7 and he eats his breakfast. He's even starting to wean himself of his 10/11am feed.
May be worth a try, if like me, cold turkey scares you!