Thanks all - very helpful responses. The 7-13 being important is particularly interesting.
DD is starting an infant school in September that only goes up to year 3, it's got an outstanding ofsted, only negative for me is having to move her at end of year 2.
She would then need to go to primary school, one option is great but very small catchment that we'd need to move to get her into (probably spending an extra £30-50k to do so, for the sake of four years of good primary), one not so great and showing few signs of improvement.
Secondary schools are good and we have grammar options. For me, Latin, MFL, music lessons are something that state schools don't seem to offer - or don't offer to the standard we'd like/at the age we'd like and I went to one of the local very good state schools and didn't find it academically very challenging, ended up becoming completely disengaged with school (probably should try and not let this influence decision).
Options are:
We could send her private now, which would solve a multitude of childcare issues short term but I would be reluctant to send her to private secondary due to cost.
We could send her private when she finishes infant school and do 7 - 13.
We could send her to private secondary school.
We could send her private all the way and take the hit on retirement age, savings etc.
We could send her state all the way.
I JUST don't know. In many ways, we're very lucky and have good state schools locally and I am sure she'll do just fine in the state system and it's perfectly possible I am overthinking it. Maybe I should just review when we need to make decision about next school.