As stated, Air UK was formed from the 4 companies, the Engineering base at Blackpool was closed in November 1980, the Herald fleet was reduced at that time, the high time Heralds were laid up and scrapped at Norwich, over the next 2 or 3 years the remaining Heralds were sold or scrapped, ( a couple went to museums). The engineering base was consolidated in the Air Anglia hangars at Norwich, concentrating on the F27-200 series operated by Air UK, customers at that time were Lauda Air, Busy Bee, Skyguard and Avianco.
The old BIA routes to the Channel Islands were still operated by Heralds up to around 1982 when the F27s took over, by then the company livery was on all aircraft and the identity of BIA and Air Anglia had disappeared.
A few customers Heralds were maintained at Norwich up to around 1990 or so, but the F27s were operating all the company routes.
Air Anglia routes were mainly east coast, something like four return flights a day to Amsterdam, and Leeds - Edinburgh from Norwich.
BIA continued at Gatwick with BAC1-11s but this was not part of the Air UK group.
I worked for BIA at Blackpool and moved to Norwich when the base was closed, much better engineering facilities - and much better pubs as well.