CAP 698 is a UK official document. So I would assume that 6076 feet IS the current UK and JAR value for a nautical mile. It is nothing personal, believe me! I will write whatever value they want me to use.
Another one is that one must use a Pooley's CRP-5 whizz-wheel. The last time I saw something like that was in an aviation museum. A Jeppesen CR-3 is much quicker, easier and more accurate but all the answers are predicated on using this antique CRP-5 artifact with its clumsy way of working compressibility into the equation. Sigh ...
The best one I have seen, so far, was a German test problem that had to be worked backwards to arrive at the Indicated Air Speed! Fiendishly difficult and totally pointless, since in the real world one glance at the airspeed indicator would give the answer to that.