[Chris_oz]

It sounds like you have checked almost everything.

with the engine off, pump the pedal several times and release, then do it again, until you have a nice high firm pedal and the vacuum is gone from the booster.

Keeping your foot firm on the pedal, start the engine.

The pedal must sink down towards the floor, this indicates that the booster is Boosting.
If the pedal stays at the same height, booster is not working.

Double check the hose to the booster, make sure it is vacuum hose, non vacuum hose will collapse and block vacuum, sometimes a small amount can get through, this is enough to trick you to think its all good.