Two extra pre-dreadnoughts and wartime availability

Would two extra British pre-dreadnoughts make much difference?

Probably little strategically, but they would help sustain complete squadrons when some ships were unavailable.

The question adds one ship to each of two British pre-dreadnought classes. The reply expects little change in the broad balance. It nevertheless sees a practical benefit in generating enough available ships for complete squadrons and command duties. The numerical estimate shifts during the answer, so the useful point is improved availability rather than a firm total of ships always ready.