The Frog 52 Single Speed was discontinued in 2021, however occasionally becomes available secondhand.
If your child has an inside leg of 52cm but doesn’t need a bike with gears, then the Frog 52 Single Speed is a good option.
You can even take the pedals off and use this bike as a balance bike, and add them back in if and when the time is ready.
When this bike was last sold new it had an RRP of £330