Have had a look at the Birmingham Post for the 1800s to see if I could find a reference to Angelus #hall. No references found. There are tow possible reasons I might speculate for the name. At the time of when the building seems to have been erected (late 1880s) there was a lot in the papers about a painting called "Angelus" by Millet, which was purchased by the French government, but which soem seemed to think was crude and unimpressive. Possibly . because it was a name in the public eye, thename was used. The other suggestion, also a bit weak, is that , at that time there was for sale an Angelus organ, advertised in the Post, by a London firm. Riley's was a music shop , and so perhaps they had an organ of this sort installed. Neither suggestion is particularly wonderful , I know, but am outting them forward. Incidently, "Angelus Hall " is not listed on either Constitiution Hill, or Henrietta St in this period.