Well they are usually found living somewhat colonially beneath bark of trees and under climbing plants such as ivy on external walls. I am not sure why they occasionally venture inside in their marching hoards, perhaps there has been some disturbance outside, a change in local environment or maybe this is just their natural dispersal behaviour. I think all you can do is brush them off into a dustpan and throw them back outside.
Personally I think they are pretty little millipedes - and sharing your name Poly.
They might be springtails .
Compare with this http://en.wikipedia.org/wiki/File:Orchesella_cincta.jpg