It's a shame I didn't know last night, I could have panicked properly then. But never mind...
http://news.bbc.co.uk/1/hi/england/7266136.stm
has full details, but it seems to have been fairly boring as earthquakes go; more intense than usual for the UK, but so far nobody seems to have been killed and only one person injured, so it could have been one hell of a lot worse.