Party ideology is not as fixed as it once was, and Ed Miliband faces the same problem that David Cameron faced in trying to determine how to establish a distinctive, ideologically coherent message that doesn't veer too far away from the middle-ground consensus that still decides elections.
A couple of useful support links for AS students are here:
1. From the tutor2u website, Mike McCartney gives an overview of where the parties are at the moment, using a recent sweep of relevant stories.
2. The Today programme's Norman Smith has a fascinating report on the problem for Miliband as he tries to recover lost constituencies like Gravesend, which still seem to be firmly in 'Blair country'.