Some callsigns stick in your memory. We used to use both RAFJET until we were told to use RAFAIR and a 4 number task number. For a given set of sorties we would have an allocated number block. For instance 48xx was allocated to V-bombers on Western Rangers. Each wing might be allocated a sequence within that block. I seem to remember that transports used ASCOT after the creation of Air Support Command. Before that they used RAFAIR with 4 number task numbers too.
In 1963 the Bomber Command Hastings used Mike callsigns. On one flight our Captain kept mutter Mike Whiskey Gin Vodka Tonic sure enough the Co transmitted that campaign
We then switched to a station telegraph plus 2 numbers with Mike callsigns for overseas In addition to RAFJET/RAFAIR.
In 1965 on a Western Ranger we had the unfortunate campaign Mike Tango Uniform Romeo Delta and the American propensity for usiencryp.
I think by 1970 we dropped the Mike callsigns. We then used a 3 character (or was it 4) for individual sorties using a particular codebook. I remember the Navy used these too but further encrypted. One such was Ark Royal SLANT SLANT ZERO SLANT is //0/