has he turned nocturnal?

[twocultures]

I'm writing this whilst drinking my third cup of coffee, trying to sort the house and tackling a moody 1yr old who decided it would be much more fun to stay awake all night last night...I feel like I'm back to square one cue the sleepless nights
He's been sleeping through since 6months (from 9pm to 7.30am) there's been no issues if he woke up the odd time here and there I'd just stroke his head in the cot and he'd go straight back to sleep but last night he woke up around 12am and kept crying in his cot, stroking his head didn't help, tucking him in didn't help, trying to get him to cry it out didn't help, it got to the point where he was throwing himself around the cot and bumped his head (it didn't hurt him but it was worrying as I could hear it from our room and thought he really hurt himself).
He's currently got 3 new teeth coming through and I thought that maybe it's bad teething pain so after an hour or so decided to give him some calpol, that didn't help. He was screaming the place down unless I was holding him and walking around with him. I was falling asleep standing up. It got to the point where I relented and listened to my DP and decided to take him in bed with us. Did it help? Nope. He was wide awake trying to crawl around and stand up, gurgling and babbling, pulled half my hair out, almost fell off the bed and ended up falling asleep about an hour before DP had to get up for work. It was so unlike him...
I've got a few theories mostly from digging up some old mumsnet posts I read that they might be awake if they're really close to starting to walk (reaching developmental milestones) and have quite a lot going on in their brains, might be sick (but he's absolutely fine now, no sings of discomfort), or might just be needy. I'd say that the most likely is the walking part as he's just about ready to set off on his own and has recently been trying to let go of the sofa or whatever he uses for support and walk on his own.

Do you think it could be something else?
And what would you recommend I do to try and get him to sleep properly again? I am determined to not let him get back into our bed.