Millpond do a book with all of their sleep techniques explained. It's worth a read and worked, in part, for my 2 who are (in comparison to their peers) rubbish sleepers. DD1 is 3 in September and DD2 has just been 1. Sorry if this isn't helping!
DD1 got a lot better once I persuaded her to go to sleep without being cuddled, or falling asleep after having food. From memory I started with the Millpond techniques when she was about 9 months old. It didn't happen overnight but within a few weeks there was a noticeable improvement in the amount of time it took her to go to sleep and the amount of times she would wake up.
TBH it's been a bit up and down in terms of success. I got her sleeping pretty well about 18months old and for about 6 months she slept through most nights from 7.30 til 7am. Then DD2 was born and all hell broke loose! That was followed by DD1's eczema playing up so she was waking for several hours in the middle of the night feeling uncomfortable and scratching like mad. Then, they both got chicken pox!
I think (speaks quietly) we are turning a corner. I went back to the Millpond book with DD1 as following the eczema issues she had been cuddled to sleep by Dad. Using the gradual retreat approach she is better at going to sleep on her own but even now sometimes needs a short back rub to feel dreamy. I can usually then leave her saying I'm going to tidy up or some other random excuse. This past week she has started to sleep in her own bed most nights and today - for the first time in ages, she managed from 7.45 to 7am!
DD2 is a different case. She has always slept better than her big sister but that wouldn't be hard as DD1 used to wake every 2 hours or so at this age! I usually get her to go from 7pm to 2.30am when she gets herself either stuck up against the side of her cot, has lost her dummy, or just randomly cross. I'm afraid the need for sleep wins to I take her out of her cot and lie her next to me in the spare bed in her room. If I'm lucky she then snoozes til 6am. Today was 6.10am but for the last week it's been 5am. Yuck.
Sorry for the essay. But I guess what I'm saying is yes in an ideal world get the Millpond clinic involved but it is pricey so give their book a go. It's in our local library and probably in yours. The trick, if there is one, seems to be getting them to go to sleep on their own. Once they have cracked that then they tend to go for longer periods of sleep at night.
One last thought. My Mum keeps laughing at me whenever I moan about my two and their sleep. Apparently I was 6 before I slept though reliably! All things will pass and I guess there will come a stage where we are dragging them out of their beds for school!!