BSA does refer to British threading so your good to go from that perspective. In my opinion the French components on the Triathlon are nothing special. The ride is very nice, later models came with Reynolds 501 tubing versus the lightweight Super Vitus the bike your considering has.
The Triathlon should have a 'P' designation, I dont know what it is but to be honest I wouldnt worry about it. Super Vitus bikes were called PSV10 and PSN10 (N=clincher tires)