I haven't read all the posts on here, but wanted to let the OP know I have done it - at the time on exactly the salaries you mention.
Before DS was born DH and I planned to both work 4 days a week with DS in childcare of some sort for three days a week. However by the time he was 6 months and it was time for me to go back to work, we'd both changed our minds. I went back to work FT and DH looked after DS full time. No judgment on childcare, it just wasn't for us. Not long after I was diagnosed with PND and was off work for a number of months.
Long story short, after far too much therapy (!), I realised that despite the official diagnosis, it wasn't so much PND as an early mid life crisis. I was 31, had worked my arse off for years and found it bloody hard to come to terms with the fact I didn't want to work anymore. Not in a stressful office environment anyway. Long story short, I negotiated voluntary redundancy.
DH, DS and I moved to NZ and DH has re-trained to be a chimney sweep (previously in accounts). Life is so different you wouldn't believe, but we are incredibly happy, albeit poor. However growing your own veg, mountain biking, snowboarding (we live near a mountain), camping, swimming, surfing, etc are not particularly expensive compared to parking permits and the congestion charge in London!
Warning: The thing I found hardest was dropping the identity and false prestige my job gave me. It may have all be false, but it was often comforting IYKWIM.
I doubt I will ever go back to a similar career, although I intend to start a business or two of my own in the next few years. What has been amazingly refreshing to me is finally realising that you can do whatever you want, I never really believed it for myself, hence good girl at school - onto Uni - onto good job in the city, I followed the exact path I was meant to.... The past few years have felt so exhilerating, because I am doing what is right for me, not what is 'sensible'.
I've waffled. Just wanted to let you know it can be done. Good luck with whatever you choose and congratulations on your DS.