I would like to train to be a singing teacher... I have a pretty good voice, know all the basics re breathing etc, have been in lots of choirs, can sightread piano well enough to accompany someone, have Grade 8 singing and Grade 6 theory (a long time ago...!) but I know lots more qualifications etc are expected these days.
Can you give me some advice as to what I would need to do?
Honestly? As a parent, I'd expect you to be a qualified music teacher. That's not me answering with my 'freelance board' hat on, iyswim, it's more than possible others will pop up with practical advice/another pov but if I was paying you to teach singing to my child then I would expect either full qualifications or significant professional experience.
I did CT course a while ago and it was very good, would definitely recommend it. I did the DipABRSM about 6 months later and it wasn't too much of a stretch (and I got an exemption from the written part for having done the CT) - I think you can do both together now. It was great for networking and getting ideas from other teachers and my tutor was fab too. Go for it!