There's probably a sticky for this somewhere. If not, I have it
bookmarked since it seems to come up regularly.
Aircraft reggie prefixes correspond to (and are issued by) the International Telecommunications Union national radio callsigns.
The UK has a number of radio allocation letters beside the familiar G-, I have no idea why the VP-,VQ- and VR- series where selected for the ahem... colonies. Queen
Victoria's Empire perhaps ?
The above list also explains why 'new' countries don't always get reggie prefixes which make sense - those letters are already in use (although some reassignments do occasionally happen).
hth