The ICAO type designators muddle the issue a bit, that is a completely separate list that was used in flightplans. From an old version: the VC7 code was used for the Viscount 700 series and the VC8 code for the Viscount 800 series but in a later update, both of these were merged into the VISC code. In a similar way, there used to be a separate code for the Standard and Super VC10s (VC10 and VC15 I think) but these were also merged into one VC10 code. I found the VANG code in an old ICAO doc, but internal Vickers documents did refer to the Vanguard as the VC9
AFAIK. I have a list of the Vickers Commercial numbers on my site too, it mostly follows the one in Andrews & Morgan's book:
https://www.vc10.net/History/vc10_origins.html