I also found Julia to be an insufferable and self centred user through all three seasons. Every group of people seems to have one like this, I'm quite happy to lose her from the mix.
Amanda has a lot more scope for development - raised to focus on looks and finding the right man and putting all her efforts into home and children she is now quite vulnerable as the big salary fucks off with the OW. In her 40s she needs to find a way to earn a living and reorganise life - its not an uncommon story and its interesting.
Love Lumley and think she is at her best in observational comedy with a slow burn on character development. Conversations from a Long Marriage is a work of genius.
Agree Mal is the Liz replacement - like the character but would be even happier to have kept Liz as well. Hope we see more of his family relationships over time.
Della and Fi - under developed, we only saw a glimps of more in the conversation with Amanda about the strains of starting a business. I hope they are rounded out in season 2.
I would also like to hear more about Anne's job and what she is now doing. I wonder if she will be revealed to have returned to GSK or similar using her PhD. Also loved the "I know this stuff therefore I can teach it" scenes - I suspect most parents have been there.
For a school in Harlesden the DC school is extremely white unless the demographic has changed dramatically in the last decade.