Thank you so much everyone for your comments. Apologies not to have been on top if this. Firstly I couldn't work out how to reply to everyone (all good now hopefully) and secondly I've been in hospital since Sunday (also all good now!).
We are very involved in our local Saturday Music Centre @Musingaboutmusic @clary , which is how DS got into music. However I'm starting to feel like it's not enough - it's progressing so much more slowly than he is. He also has a 20 min a week instrument lesson at school (previously recorder, now starting flute) - also not enough.
@mamagogo1 He's not a great singer I don't think but he does love to sing! I don't think a choral school would be the way to go although @anotherfinemess1 your school sounds absolutely wonderful.
I will search for schools that do the Musical Aptitude test, thank you @Op1n1onsPlease that's a really good idea. And it's really good to know about Dame Alice Owen, Ashmole and Latymer @Jumpingthroughhulas - I think DAO was the school I'd heard of but couldn't find * *and didn't know about the other two, thank you. Will look into it.
@Ubertomusic He plays the recorder and is now moving onto the flute. I hadn't heard of YMC* *and it looks great, thank you. I've looked at Guildhall CYM, the Primary Academy at RAM and the Junior Academy at the Royal College of Music (which looks like the best fit for him). All look intimidating and difficult to get into but I'll give them a call and see what's realistic.
I think for now I will look into a more challenging Saturday provision and will also look into all of those school options, thanks again everyone for taking the time to reply.