I agree that the relationship has broken down and you would be better off finding someone else to mind them.
However, I wouldn't mind her taking them shopping, even her food shop for Christmas. So it was borng - life isn't a funfair - best they get used to that idea now rather than think the world revolves around them.
I wouldn't mind her DH staying in the car with my DD. Frankly, CRB checks aren't worth the paper they are written on, but I thought for CM's all members of the household over 16 were CRB'd (is that not the case?). One of the reasons I would choose a CM over a nursery would be to have this kind of a set up. Kids doing normal day to day jobs, occasionally doing something boring like supermarket shopping for Christmas.
As for waiting outside for you, if you hadn't called to say you were running late and she'd got their coats etc on they were probably too hot inside. Yes they were looking a bit fed up - they were waiting for you!
As for the charges - I presume she is then available to you to collect the children if they need to be collected from school/nursery due to illness etc & that she has them in the holidays/inset days etc? You are paying for her to keep the space for you. £90 a day works out at £4.50 per child per hour - the rates will vary from area to area - but would you look after someone elses child for less than £4.50 an hour?
I think you are being unreasonable on all counts except for the road condition. I don't know where you are. Our roads are fine today, just wet, no worse than if it had been raining and I imagine most main roads would have been fine with the exception of a lot of Scotland - so I don't know if you are BR or BU with regard to that.
If you change childminders you need to make sure you are happy with all of the terms & conditions next time and that you talk about what you are and aren't happy for the children to do and if the CM agrees then you both know where you stand.