Have you tried Italy?
Sorry for being flippant, my first bike (secondhand) was an Atala equipped with 4-speed Simplex gears, steel chainset with Atala name engraved but probably made by Gnutti, Pivo bars and stem. It was probably built around 1952 and I took delivery in 1959 and rode it with a few alterations until about 1964.
Try contacting Atala in , I think Turin, and ask them for details of suppliers in UK.
They used until a few years ago , sponsor a road team , Urs Freuler of Switzerland was one of their stars , even long before that Vito Favero 2nd in TdF about 1957 and Vito Taccone winner of Tour of Lombardy 1960.