This link has the words to The National Anthem of the Ancient Britons which are more as I remember them. I learned it around boy scout campfires by proper folksong oral transmission, but it seemed to have undergone very little if any change from the published version.

The final line, "Go it, ancient B's" was criticised in this thread as being rather awkward, but I feel it is preferable to the "W O A D Woad" line given in the Digitrad, which doesn't rhyme with "fleas". "Go it!" was a rather schoolmasterly expression of encouragement which sounds rather old-fashioned now but is exactly right for the period when it was written, as are the spats and hats.

I have never heard the "Bollocks to the breeze" line quoted in the other thread and given as an alternative in Digitrad. This certainly wouldn't have been in the original, which was written by a schoolmaster at Eton in the 1920s for the school's scout troop. It has a certain robustness but doesn't to my mind naturally follow from the preceding lines.