Do you have to have them at all in a private house in England? I mean builders may be required to put them in but does the homeowner have to keep them?
The definitive answer is that the handrail top must be between 840mm and 1000mm above the pitchline in Scotland. The pitchline is the slope by putting a straight edge on the front edge of the top of the risers.
England and Wales differ, and the relevant dimensions are between 900 and 1000mm