Harman, I didn't read this thread because it's in the lone parents section, and I'm not a lone parent so I didn't think I'd have anything to contribute. Had I known it was you I would certainly have posted something to try and cheer you up a bit. Do you not think that there must be lots of your mn friends who wouldn't always even read certain messages in certain topic areas? Post on chat next time!
I have been where you are and it's not pleasant trying to get used to the new status quo. Perhaps it might be an idea to get a formal agreement about ex p's contact with the kids. Then you'll never need to worry about his disappearing with them. If he ever tried anything you would be able to prove that your kids should have been back by a certain time and get immediate backup from the police if he is ever late.
In the long term, you might enjoy the freedom that their visits with him afford you. I used to go out and not worry about what time I got home, sleep late in the morning, have friends round etc.
Please DON'T feel guilty. You did what you had to do and with you to love them your kids will be fine. You know deep down that for them to live with warring parents was no good. And your happiness is important too. You can be a better mum if you are happier, and you will be happier now you have your life back.