All percentages are “up to” values and I imagine you would need to be exceptional to get that much.
St Albans High School (Day) - 50%
Habs Girls (Day) - 50%
Eltham College (Day) - 50%
Roedean (Day & Boarding) - 40% if combined with great academics
Royal Masonic (Day & Boarding) - 25% officially but I know someone there on 40%
Pipers Corner (Day) - 10% standard, up to 50% for exceptional candidates
I used to audit bursary applications and the great majority awarded went to those children who had been offered either an academic or music scholarship too, with the bursary being used to top up on a means tested basis.
If your child is an extremely talented musician then it’s worth asking the bursars at the schools you are interested in that are only offering, say, 10% what their criteria is for bursary eligibility. In some cases it can be earning less than £100k.
As the parent of a boarder I can honestly say DON’T DO IT unless your daughter wants to do it. If she’s not keen then it can be a recipe for disaster, however good a school or financial incentive being offered to be there. I know for some parents that boarding is a necessity, but it can be an extremely miserable experience being sent away when you don’t want to go.
I would add that my daughter begged us to weekly board and absolutely loves it. For us it works exceptionally well and she is thriving.