It's funny that I saw this thread because Georgie has started waking up in the middle of the night again. He hasn't done this since he was 5 months or so (he is 14 months now). I just get up with him and we go outside. Our yard is fenced in but I don't let him out by himself and our boxer Coco is definitely not willing to get up with him LOL. I have to ditto what Rebecca said above I am just happy that Georgie gets up and lets me know he needs to go out. On the rare occasion that he can't wake me up he leaves Mommy a nice little present on the floor in the morning
Some people may suggest not feeding him or letting him drink water after a certain time and you may want to try that. Me personally I want him to eat and drink when he feels like it since he is such a small baby.