This lad seems convinced, anyhow.
It's quite likely. They were certainly breeding in N Yorkshire a couple of years ago, according to this BBC report.
The World Owl Trust says: "We regard the confirmation of the Eagle Owl as a resident breeder in Britain as an exciting event on a par with the reintroduction of the White-tailed Sea Eagle and reinforcement of the Red Kite population..."
Amen to that.
I'd love to see one. I wonder if they take magpies, the local bullies of the birdworld. The arrival of bubo bubo would be like the arrival of a Terminator. We could stand to lose a few pigeons, too.