Wow, you're all such a kind and caring bunch! Sticker charts, looking under the bed for monsters etc. You make me feel really hard hearted.
My 2.5 year old son is going through the same thing as you, bugsy and phb, marina, lizzer, motherofone... (phew! have I forgotten anyone?). We havn't had the monsters to visit yet, but we have had lots of interrupted nights in the last few weeks. Our son can climb not just out, but also into his cot bed, with casual ease. Two or three times a night he was wandeering into the hall and either announcing that he was wet (he hates a wet nappy - fair enough), or that he's 'lost it'. He wouldn't say what he's lost, but once he had your attention, he'd look very crestfallen and would start wandering around vaguely. Not what you want at 3.00 am. Dh and I came very close to 'losing it' too!
I think the overriding reason for his wakefulness is that he's growing out of his day naps. Is it just coincidence that so many of us have found that age 2 and a bit, night sleep becomes fitful?
IMO looking at my son, the main cause is physical, not mental. The 'lost it' anxiety is just a symptom of this. I hate to say good bye to the two-hour day nap, and welcome breather for me, but it's got to go. He is now having 40 mins at the most and sometimes nothing at all. Although he sleeps well at his childminders, I have asked her to do the same thing.
We are using other tactics, some nicey-nicey, and some not. I'm saying 'we' but actually it's my husband - the light sleeper - who has suggested these things, not me.
He said 'look at his scruffy cot blankets, machine-washed over two years, so they are really thin and manky. He must be freezing. We've got to make his bed an attractive place to be'. So we've given him a pillow, new softer sheets and an expensive fleecy cot bed blanket from mothercare - £24.99, can you believe it! I've tucked it in to form a little nest. My son calls it his quilt and now refers to himself as 'Queenie' - he's got an ABC book and Q is 'Queenie has a Quilt'. He's into royalty in a big way and likes having a red bath towel draped round his shoulders so he can swank around etc saying -'I'm ROYAL'. He's got the genders a little muddled up, but so what? Anyway, the bed enticement tactic is working.
But I'm afraid we are not just being all nice about this. Again this is my huband's suggestion, so address any cries of derision to him, not me (I protested much when he suggested this): After his bedtime routine, we are allowing him one plea of sleeplessness - I might change his nappy, give him an extra drink etc - then we tell him we are locking his bedroom door, which we do. Grumbling, very low level cries follow for about 10 minutes, with some scampering around in the darkness of his bedroom, then he apparently gets fed up and hauls himself back into his bed and nods off. As soon as we have silence for five minutes, we check to see if he is asleep and we unlock the door again. The same thing happens if he's up in the night - he's allowed one or two pleas of nappy changes or a drink, often ends up in our bed, but ultimately he gets locked in his room for the 10 minutes or so it takes him to go back to sleep. I was staggederd by how little he was upset by the locking in.
That, and the fleecy quilt seem to be doing the trick. Though I think the lack of a day nap is the underlying reason for the gradual improvement.
Many sympathies, Bugsy. Hope you get this sorted out before your new one arrives.