Servo or reaction valve?

[Stevejaguar]

Series 1 4.2 2+2 1966.

Usually, if I press the brake pedal hard and then start the engine, the brake pedal goes down slightly.
When I switch the engine off I usually get two or three pumps of the brake pedal exhausting the vacuum
from the system.
Neither of these is happening now.
What I have checked is the following.
With the engine at idle there is vacuum at both pipes to the servo. As the brake pedal is depressed the vacuum is lost to the air side of the servo ( F in the manual).
With the engine not running I can blow through the pipe from the air side of the servo and air comes out of the filter on the reaction valve.

The brakes feel 'dead' just like there is no servo effort at all.
I havn't had chance to road test it but am confidant that the brakes will be useless.

Any ideas on if its servo foo or replace the reaction valve?
Does anyone know the correct length for the master cylinder pushrod as I seem to have two.

Steve