I joined BOAC in 1962 as a pilot but had to get my Flight Navigators Licence on Britannia 312s. The training was done by the few remaining straight navigators. After 2 years I went to VC10s as a pilot/nav. The crew then consisted of a captain, 2 co-pilots who alternated (roughly leg and leg about) between rhs and the nav table, and a flight engineer.
I can confirm ExSp33db1rd's recollections, though being on VC10s we did not have to do polar navigation. Everything else was the same re Loran, Consol, astro, etc. You have a wonderful memory! I can also confirm that the lateral separation on the NAT track system at that time was 120nms.
INS was gradually retrofitted somewhere around 1973/4, thus we were able drop the additional co-pilot and revert to 3 man crews. I became a navigation instructor and also a check navigator in the VC10 nav office in the same corridor in the Kremlin as ExSp33db1rd!
Building 221 was on the north side of the airport as confirmed by George,etc,etc. It was a 2 story building set amongst a number of similar buildings. Crew reporting was moved to Terminal 3 soon after it opened in 1961, but was still called it 221 for very many years.