Hi, my DS - Year 7 - is very musical, bright and also not very sporty.
Until Year 5 we were at Pre Prep and Prep at St Faith's. We were reasonably satisfied with Pre Prep there but not at all happy with the Prep school. Overall, I'd say it's not a good choice for a child who isn't esp sporty. Music is quite good there but he's had more opportunities to develop his musical interests since we left than he did whilst there. Whilst at primary school, some of those were made via private music tuition options and holiday clubs, although, now he is at secondary school there is plenty of music in school for him.
Stephen Perse has a good reputation for pastoral care these days, likewise King's. Music is very good at King's, as one might imagine. Stephen Perse very good for the quirky child, which mine definitely is.
One thing I will say I think is better in the state sector is 'help' in almost any form relating to emotions. Our experience of pastoral care and sympathetic handling at primary and secondary level simply isn't in the same league as the judgemental nonsense we experienced in the private sector. All schools - whether state or private - are different though, so it may just be we got lucky after suffering the purgatory of the Prep School.
If any SENCO or Learning Support is needed, I would say the state sector is best. Simply because it's ultimately more about how one uses Learning Support resources and views the concept than it is about finances. I'm not assuming you need this, but it's my observation this is an area linking into pastoral care and the ethos is very joined up in our experience of the state sector.