disco brake issus

HI ALL
HELP trying to work out what is wrong with my brakes, no further forward at minute
disco 1 200tdi none abs.
here goes
brake pedal goes solid when driving no brakes
have replaced brake vacumn punp unit
brake servo . taken master cylinder off cleaned flushed out refitted
servo oneway valve
checked all calipers are working freely have replaced rear flexi , rear brake lines

what am i missing
any throughts ideas would be greatfully recieved
many thanks
dave

Is the vac pump making a vacuum?

i think so did replace it with a second hand one,
is there a way of checking to see itf it works

yes vac pump is working

A quick chech to see if your servo is working is with the engine off pump the brakes untill you have a solid pedal, keep pushing the pedal, then start the engine, the pedal should go down further this shows the servo if working