Its easy - go to the schools nearest to your home and look around them. Ask questions, read the Ofsted reports, look at their stats and standing in the league tables for KS1 & KS2 SATs (if you are so inclined - I'm not).
Are you aware that your DD is especially bright (we all tend to think they are, esp first children, until they get to school and mix with other kids, and we may find they are not quite as exceptional as we thought). If you are putting her in a selective independent she needs to be able to manage it emotionally and educationally. Is she a strong character or the shy retiring type, who might be better in a less selective school.
Lastly fees are a massive commitment - you will be looking at more £120-£150,000 over the next 14 years to the end of education, and THEN university for four years. No point starting if you will have to pull her out and change schools if you have a financial crisis or baby number 2/3 comes along.
If you live in a pleasant area, populated by largely middle class profs/semi profs, your local schools should be fine. Bonus is you can walk to school, your DD can go to a local childminder or after-school club if you work, you shouldn't get bogged down with masses of homework at weekends like some preps give, and your DD will have local friends she can play with and have after school play and tea dates with - those are the sort of things a memorable and happy childhood are made of - some freedom to play. Local friends are important - ms DS1 is 20 and will be found out and about with people he was in reception class with as well as those he has met through work. DS2 went to an independent senior school miles away, but he still mixes with all his old friends from infant and junior school because they all live around the corner, esp this summer while he and they have had the long summer post-GCSE.
Think less about academic achievement and more about personal happiness, because the former is meaningless without the latter IMHO.