Hi Kay. I tried to write a reply last night but I'd had a couple of glasses of wine and I couldn't get my words out

Firstly, I wanted to say that you are not on your own, however much it feels like it at times. Remember that when things get tough xx
Secondly, I think your mum will bad mouth you whatever the situation, whatever you do. My feeling is, if I'm going to get bad mouthed I'd rather get bad mouthed for doing something that is healthy for me than bad mouthed for anything (everything) else. It takes courage, and it isn't nice to know you are being slagged off, but boundaries are there for you, not for anyone else and anyone who doesn't respect them doesn't deserve time/space/energy from you. It's easier said than done (and I still have trouble with boundaries) but you are doing this for the right reason and is does get easier with practise.
I think writing a letter is a good idea but.......................be prepared for them to ignore it! Perhaps look at it from your own perspective, make writing the letter about what you feel is right rather than what you hope their response will be. So, being the normal person that you are, you want to put your cards on the table calmly and let everyone know what the situation is. I think that can help (you) and I think the wording you've suggested is pretty much spot on. I'd be inclined to think that she won't respect what you want though, so plan B will be turning them away if/when they turn up again.
You can go for the down key approach (oh! We're just on our way out. You should have called, what a wasted journey for you, bye!) as you bundle everyone into the car and vanish. It's slightly easier than outright confrontation but has the disadvantage that you still disrupt all your plans and they might be there when you get back, or decide to stay nearby and turn up again in the morning.
You can, as Bonesie suggests, be really rude

I've really let rip at my mum before and I know others have. It gave me a release that I still can't quite put into words but............you have your kiddies and if they're there you might not want to do that in front of them.
So your third option would be next time to say "Hi. I've already said it's not okay to turn up unannounced. It isn't convenient. You need to go home." or however it feels best for you to word it. And then go in and shut the door and just carry on like they aren't there.
It is incredibly hard, Kay, any you'll probably feel guilty and like the worst person in the world for doing it but, to be honest, if they're daft enough to do a three hour drive on the off chance that you're going to be home and available then that's down to them. I don't think there is a nice, easy way to distance yourself from difficult family, there are mind games, emotional manipulation issues and that horrible tug between wanting a family and not wanting the one you have!
And I do understand the way you feel about your hubby saying he's fed up with it all, I've been on both sides of the fence and it's so tough for everyone involved. Is he in your camp on this one? Does he want to stop them coming over like this as well? Perhaps the two of you, on the lawn together saying the same thing next time she comes over might help? Some people find a time limit to talking about it helps - ten minutes a day and then you get on with something else? Boundaries again - don't let her keep taking up your time, your head space, your relationship with your hubby, your lovely babies. It's hard, you have to kind of re-train your brain and that's a lot of work but it does get easier.
I hope that's not all come out as gibberish. It's early and I haven't had any coffee yet

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