I should add that I have two girls and at 7 the OnOne was slightly too long for the youngest and I bought a Luna from Halfords. Stripped it completely apart from frame/wheels and bars, replaced all the heavy stuff as above. Its a good light frame and the wheels are fine.
It was unbelievably lighter when I’d done. (If you don’t want to use forks the 440mm a2c OnOne carbon forks fit a treat and barely change the geo at all with 24″ wheels)
Then when she was a bit bigger I put all the original stuff back(unused) and sold it like that) and put the running gear on a new OnOne frame.