The UK rule is/was no double medalling i.e. service(wo)men should not be issued with two medals for the same period of service, This has occasionally been relaxed for diplomatic reasons to allow acceptance but not wearing with permission from the monarch, UK personnel were also issued with the UN Service Medal Korea but could only wear the UK one (my late uncle told me he thought it stupid that he couldn't wear both). This was the reason no UK medals were issued for the 1990 Balkan 'campaigns' as there were already NATO and UN ones. There was a review in the early 2010s that recommended abolishing the rule , not sure what happened, (Crossed with LJ's post)