They sound like silverfish to me, by your description. Have never seen them before apart from when i was living in London. I spent ages trying to figure out what they were.
From what i found out they are totally harmless but feed on paper, so beware any books that you might having lying around.
Good thing to squish on sight as being sucked up by a hoover doesn't seem to kill them, i was mortified once to still see a few of them crawling around inside the hoover.