Just the three main tubes are 531 db, the rest ist 'high tensile' (whatever they might have understood as 'high').
The Team Rapides were made in England for sure, they have the flag sticker at the bottom of the seat tube which makes that clear; the one pictured has this writing in the middle of the top tube that should say "Handbuilt in England". I think I remember Rapide serial numbers beginning with the "Worksop"-W, but I could be wrong with that.