That's not exactly true. The SA80 isn't exactly new. It was in use during the Falklands for example. And the British Army used a version of FN FALs before the SA80s were adopted, and those were also automatic rifles.

Now, I'm pretty sure 'automatic' fire was burst limited. But that's pretty much nearly universally accepted as a good idea in main infantry rifles.

The LSW variant has always been fully auto and is 25 years old, and the L85 is to this day semi-automatic and is the main rifle in use in the British army. I don't see how they've "only just relented". Full auto isn't that useful anyway! The ability to empty your magazine in a second comes in handy less often than you'd think.

In fact the US Army's M16 was changed from automatic to semi-automatic, so it seems there is a movement in the other direction.