pump over run ? ?

I have a Worcester Bosch junior Greenstar 24 i (2008) - noticed it's not turning itself off like it used and keeps waking me at night with a loud hum and vibration. I`m used to it "modulating" in the background but this is noiser. It also keeps running when bolier is turner off and even turned off at electric isolation swtich. The only way I worked out to stop it is hitting the mains.
Could this be the pump over run ? Is it dangerous? What causes it and hoe long should it run for ?

Thanks