jjimm, if you were near Oxford at the time, check this link for a list of recent visible passes of the ISS. If you remember when you saw it, see if any of those date/time combos matches up.
There’s nothing that says for sure that you saw the space station, but since you said it was bright, it’s a likely candidate. You can see satellites nearly all the time in the sky if you’re looking in the right place, Look up on a clear night for five minutes and watch for motion, you’re bound to see one or two. But most satellites appear no brighter than a average-to-dim star. But they do typically traverse the sky over the course of a few minutes.
However, if what you saw was as bright as the brightest stars in the sky, or even as bright as Jupiter (which is very prominent right now between sunset and midnight, and the brightest thing in the night sky other than the moon around that time), the ISS is one of the only “moving” things that would be a candidate. So I’ll guess that’s what you saw.
It could have also been the Space Shuttle if it was since August 8. But Heavens Above’s past dates for Shuttle passes are wacky, because they’re calculated from current orbital parameters. So it shows visible passes before the Shuttle even launched, and they always match up with ISS passes since they’re currently docked.
ETA: I shoudl also mention that you can see from those pass predictions on HA how long the ISS remains visible. And you can also use the altitude and azimuth numbers to figure out where it starts and ends. From those, you can see that it typically takes about 5 minutes to make it from one side of the sky to the other.