I'm at my parents now. Thanks to the posters who answered my question about petulance, I had a think about it on the walk here and I can see now how it might have come across.
I think you sound petulant because a lot of people parent with no support at all and your first post sounded like you were grumbling about what many people regard as amazing support.
Yes, I can see that. Honestly, I was grateful for them picking DS2 up, I guess I just didn't see why they couldn't have stayed for a coffee and chatted with the kids. But then I was forgetting that actually they are very much like Piffle's parents, in that they are quite regimented and routine led.
I don't understand why you think your mum was annoyed?
I thought she was annoyed because she sounded really annoyed. The first thing she said to me was "Why aren't you answering your phone?" in an angry tone and then went on to say "and why have school even got dad's number in the first place?".
We've just had a chat about that and apparently she wasn't angry (she really did sound it though!) and she's happy for school to contact them in future.
She probably just had things to do before going out and wanted to get home. You're totally overthinking and trying to ascribe complex motives when it was probably just something simple.
I think you may be right, I have form 
I said petulant because your post about being more grateful sounded martyrish tbh
Noooooooo! I really don't want to be martyrish, I will have to watch myself on that one.
Piffle, my parents sound very similar, and yes, I wouldn't care particularly but my DP go on about how they wish they could help more and tell people how much they do for me ... neither of which is true. this winds me up no end. It's the lying that gets to me, I just think that if everyone was a bit more honest then life would be so much easier.