Just read a piece in Wales online too - skies of Swansea were full of military hardware as fighter jets and helicopters passed over city. They certainly made us take notice this morning!
I heard it too. It was about 9:05. I looked on the Flight Radar app and there was no commercial aircraft within 40 miles so assumed it was military. The odd thing was from the sound it was obviously a jet and fairly low in the sky I think but you’d expect it to clear the area quickly and the noise went on for a good couple of minutes (time for me to hear it and note it was unusual, go outside to look, realise it was cloudy and go back in to get my phone to check Flight Radar).