The Royal Navy's answer to Plan Z was continuous replacement

Why did the Royal Navy lack a public fleet plan comparable to Germany's Plan Z?

It already had a large fleet and relied on continuous replacement and responsive expansion instead of building from near zero.

Britain already possessed a global fleet, so its equivalent to Plan Z was a rolling program: King George V-class ships, Vanguard, then Lions, with infrastructure upgraded alongside them. If Germany accelerated, Britain could enlarge the Lion program and exploit a construction base capable of several capital ships for every one or two Germany completed. An established fleet did not need a dramatic plan for expansion from near zero; it needed continuous replacement and the ability to respond to competitors. The absence of a British document resembling Plan Z therefore does not mean the Royal Navy lacked a force-development strategy.