I had a similar situation once... two babies in back of car, no parking spaces. Found a p&t one was about to be vacated. Couldn't believe my luck. To alieviate pressure on queue behind I swung to the right of the space, indicated, and waited...
Cue a stupid bag jump out of her car and self importantly hold up the traffic as she gestured for her henpecked dh to swerve in and take space from left. Couldn't believe it. I reversed back and stared disbelievingly as a couple in their fifties / early sisties jumped out of said car with grandson who looked about 9/10.
By then, dd2 was screaming and I was almost crying with anger. I said, "excuse me but I was clearly waiting for this space for ages." When the woman who looked like a respectable Daily Mail reader didn't know what to say she...
Stuck two fingers up at me and said "Oh fuck off" [anger]
I was so gobsmacked I said something sarcastic like, "Oh that's such exemplary behaviour to use in front of children" and accidentally wheelspun off. I had to stop in a layby on way home to cry to my mum over the phone about it!
Anyway, I really wish, if I could go back in time, that I'd let her tyres down or something done more as I still get the red mist whenever I think of the stupid cow even now (nearly 7 years later!!)