I can see that moving back to to UK will deprive the kids of their dad, so whilst posters will suggest it...not that easy
some options to think about
Teachers can change role fairly easily, are there any cities in your country where you think there might be more like minded souls
are you using the time when he has the kids to follow up on hobbies and things that make you happy, and really make sure you do
are there any new things or learning topics you are keen to do
are you exercising enough , getting fresh air and decompressing after a shit day at work
do you think there might be like minded souls in the expat community, who not try and make an effort and use the dad and Grand to cover you
lastly with the kids - do you think they are picking up on your mood? Mine are worse when I am tired
sometimes we can make some very small steps and changes, and although nothing has changed- we can be alot happier. It takes work though
Also baby steps here, 1 positive action per week