I heard on the radio about this issue and set about changing my passwords. It was a drag having to change all the connected wifi devices to a new, long, complicated password; but it was finally done.
I had already changed my default Superhub 2c password but I thought I would do it again in line with the instructions in the latest Virgin Media advice. It said that I should change wifi and hub passwords to over 12 characters with letters, numbers and symbols. Sadly, my hub password will only accept letters and numbers, upper and lower case, and no more than 14.
Virgin Media should have contacted customers with the need to change passwords; and its advice should have been consistent and correct. Are there any more default settings that need changing, other than these passwords?