Number of naps at 16mths

So can anyone help me work out how to transition Elle to 1 nap? I'm convinced that her night waking etc is because she either has (a) too much sleep during the day (days when she has 2 naps) or not enough (days when she does her morning nap but not an afternoon one).

I'm trying really really hard to increase her morning awake time but the longest she can stay up is 3.5 hours and usually it's only 3. That means her first nap is at 10 or 10.30 until 12 or 12.30 and by bedtime she is overtired and has an unsettled night. If I offer a catnap in the afternoon and she takes it she is not tired enough.

The gremlins only recently started having one nap a day, to start with we had to put up with an hour of them being tired and feral between 10am-11am coz they were tired but we'd push them out till 11am before we'd give them a bottle and put them down and now they sleep till around 1pm/1.30pm. They usually still turn a bit feral around 5pm when I'm getting dinner ready but then dinner and bath distract them and they last until bottle and bed around 6.30pm.

If you want to try transitioning IMO the best way to start is to try and push that morning nap back a bit so that eventually she is staying up longer in the morning. You'll prob have a few days of grouchiness as she settles into the new routine but it will pass.