sleep, dagnammit!

We've got to tackle the night feeds. Our seven month old is having two full feeds a night. One at 2am and one at 5am. This means he can drink almost 1 1/2 litres of milk a day. Considering he should be having about 600mls or about a pint- its a bit much and is definitely taking the edge off his appetite for solid food.
There are three ways we could do this. With Ez we went cold turkey, and I just stopped breastfeeding him in the night. He still had a 5am feed until he was 1.
The second method is to gradually reduce the amount of milk we give him at each feed- (I can't see how this would work, as knowing our Seth he'd just wake up more frequently.)
The third is to offer water instead of milk. I tried this the other night and he drank 100mls of water and stayed awake, laughing until it was time to get up for his breakfast. I would quite happily leave him to laugh in his cot and zonk out if it weren't for the fact that he shares a room with Ez and once Ez is up- there's no getting back to sleep ("I awake now! I can't close my eyes, they're broken!")
In preparation I've been stuffing the kid full to the brim with food and milk during the day. To the extent that he vomited his entire feed up in his cot the other night- then promptly demanded more milk.
They're not meant to be hungry in the night at this age- apparently its just a habit. Seems my baby's habit will be a tough one to break.
Wouldn't you just know it.