An eight year old thread but why not?
Blackrosie said what I wanted to say, about superposition of Christian worship sites on pagan sites. The significance of the latter remains to be seen and we will have to rely on archaeologists to increase our understanding of how pagan settlements functioned, on a day-to-day basis.
When ancient Britain was still heavily forested, any small hill would be valued as a look-out and, after forest clearance, if it was too awkward for use as farmland then it could be used as a burial site, or a moot (meeting place). Sooner or later, someone will assign spiritual significance to it and it will still be the place of worship by the time Christianity arrives. Who knows? Other chains of events are just as likely as this conjecture.
One way or another, some settlements in Britain have been in continuous occupation for over 3000 years, so their places of worship are, indisputably, ancient. Why that should make a difference, I can't even guess.