Albion
I recall from my spotting days at BHX that in fact, the regional divisions of BEA at the time (BEA Channel Islands and BEA Scottish) both used the IATA flight prefix BZ and the callsign Albion.
Viscounts were painted with "BEA Channel Isles" and "BEA Scottish" titles.
I can't actually remember Cambrian and Northeast divisions using Albion, probably because they didn't frequent BHX.