Such an interesting thread. You sound very sensible and clear sighted OP - your DD is lucky to have a parent who ‘gets’ her as much as you clearly do, and who has thought all eventualities through so thoroughly.
We’re in a very similar boat, albeit coming at things from a slightly different angle. DD is in Year 1, clearly bright, top table in her class (probably top 1/2 within that), exceeding expectations for everything, fluent reader etc. She has been described as ‘exceptional’ by the teaching staff at her school.
However… given that she’s only just turned 6 I’m trying to determine how much of this is genuine ability (DP and I are both pretty academic) and how much is DD’s fortunate circumstances - I’m an ex-teacher, have very much been around for her during the preschool years, and due to my own professional knowledge and experience DD was prepped extremely well for school. She also seems to be in quite a challenging/low ability class, so I’m not sure whether it’s just a case of her being a big fish in a very small pond at the moment.
We’re also in North London (albeit in a different borough from you) and we also have Latymer as pretty much the only secondary option that appeals to us. Both DP and I went to Latymer and loved it, and I want a similarly positive secondary experience for DD. Like you, we want to find somewhere that suits her but don’t really want to hothouse, and if Russell Group/Oxbridge isn’t the right path for her then that’s absolutely fine.
If Latymer isn’t looking to be an option then we are also potentially looking to move, as the comps where we are just don’t float my boat (our most likely option is a super strict academy which, for me, isn’t ticking the happiness/well-being boxes, plus none are particularly strong on arts/music, which are important to us). While on paper it seems utterly ridiculous to base a decision on relocating on the academic abilities or otherwise of a 6 year old, I know from having watched friends do it that the whole tortuous moving process means you need to set the ball rolling earlier rather than later.
I will say, having taught Year 1 for several years, that the children who I identified as being the highest achievers generally did end up being the ones who ultimately won places at selective schools. Notably my two top table ‘Latymer material’ children from one particular class both ended up there (as did the precocious one who, when I asked if anyone had any questions about what to expect in Year 1, said ‘Yes, when do we start learning single sciences?)!