Some nice Pathé archive footage of the Herald being prepared for the SA tour here:
Uk: "Herald" Jetliner Prepared For Prince Philip's South American Tour. - British Pathé (britishpathe.com)
As well as G-APWA (which now resides a couple of miles up the road from me), a second aircraft (G-AODF, the second prototype, originally flown as an HPR.3 with 4 x Leonides) was involved in the tour to a limited extent. Neither aircraft actually served with BEA.