You are going to be fine. You are having last minute jitters and the fear of the unknown is eating at you. Breathe! Once you are back in the UK, give yourself time to grieve. Right now you are operating on automatic pilot and w/the holidays coming, well, it's going to be a lot of running here and there and everywhere. If you can tolerate your family being around you a lot this holiday season, by all means allow them to be there for you.
As for your h coming to rescue you and tell you stay, he's in MLC and it's going to take a while before he realizes that you've actually moved and wont' be returning. Your son can call you or even come to visit and vice versa w/you.
Please try not look at this as a crazy idea or your part because truly it's not. You are returning to the family fold, so to speak, where you will have plenty of support. I look at this as a new page, new chapter in your book of life. Get ready to open the book to Chapter one and start filling up the pages w/new adventures and experiences. You just never know what the man upstairs has in the way of good things coming your way.
It's going to be okay! Breathe!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.