Maybe there's something going on in the general dog world. My dog - 5 years old - has never been one for wanting to go out for a wee in the night but just recently she's also started barking to be let out anywhere between 2.30 and 4.00ish.
My DD, when I told her, said I should just ignore her, but you can't can you? She had a horrible stomach thing several months ago and was pooing every hour or so, if I'd ignored her barks to go out poor little thing would have ended up going in the house, as it was she didn't have one accident in the house; I was very proud of her.
She also doesn't seem to be in any hurry to wee and will often only go after I've told her to hurry up, but often she'll have a wander round and inspect leaves and stuff.
She loves this time of the year with the cold, and strong winds - double coated - and will often take herself into the garden in the evening and have a wander round or just sit or lie on the garden path. I assume she's cooling off as she's not happy with a warm house - heating's not on at night though.
Sorry Join, I know that's no help, but I don't know what the answer is either. Putting her on a lead is a good idea, but I don't clip her lead to her collar, and I think she might find it really strange and uncomfortable, so that wouldn't work for me.
Hope you find a solution as it's horrible having broken nights. Just thought I'd let you know you're not alone :)