I feel so much for you! It really sounds like you are at the end of your tether.

OK, so I will preface what I am going to say by saying that my advice and experience of this comes solely and completely from watching Super Nanny every night whilst trying to feed DS his bedtime bottle. So it could be kind of half-baked- take with as many grains of salt as need be.

What she seems to do is just keep putting the kids back in bed. The first time she will talk to them and explain. The next time its just a short thing, like "its time to go back to bed". Eventually she says nothing at all to them, just puts them back in bed. She just keeps doing this until finally they stay put and fall asleep. In some shows the parents have to do it like 30 times!! Ugh. But eventually it seems to work. It does seem to be slightly older kids she is doing it with, but the principle seems to make sense to me as its similar to what I do with DS when he wakes up because he's crawling around the cot- just keep going in and putting him back down with no eye contact, talking etc so there's no reward to getting it, and eventually he goes back to sleep.

So, if that helps at all, take it fwiw. It looks so kind of easy when she explains it, but I bet IRL its way more complicated!!

Best of luck and big hugs.