Norse Gods/religion?

We get our days of the week from several Norse Gods, via the Viking Invaders - as in Sunna (Sunday), Mani (Monday), Tyr (Tuesday), Woden (Wednesday), Thor (Thursday) and Freya or Frigg (Friday). The only odd one out is Saturn's Day which is undoubtedly Roman. They must have been significant in the UK at one point to have become such a fundmantal part of the culture without being displaced, particularly with the kind of anti-pagan sentiment one meets in conventional religion.