I should have asked my friends with children for the truth about what the hardest parts were about being a parent. I only really spoke to them in depth about it afterwards.
Looked into nurseries earlier, I realised with a newborn that round us nurseries were pretty much full and had to spend the first couple of months looking into it when i had better things to do!
Gone on more city breaks. I think you can do lots of holidays with young kids but city breaks are tricky and I know they won't enjoy anything about them for years
Bought everything second hand. I do now but at first when you're expecting a shiny new baby you want shiny new things. It's only afterwards you realise you are selling something you bought for £50 and used for a week for a tenner and you could have bought it for a tenner and saved the rest
I'd have researched good catchment areas as we moved just before I got pregnant. Into a school with a 'good' ofsted rating which I thought meant it was actually good. It doesn't. Good is the minimum standard and there is massive variation between the top and bottom end of good and now we either have to move again or find another solution.
I wish I'd appreciated my body more as although it's not awful it will never be the same again. I should have taken some photos or something.
Also this is a bit random but I wish I'd noted down names I liked over the years (you know when you hear one and think oooh lovely name then forget it). My mind seemed to go blank in pregnany and I have quite big regrets over one child's name
I should have also volunteered for a lot more travelling with work as it's much trickier now