Looking at the votes for each candidate, it appears that the Conservative vote held up very well: compared with 2008, we lost hardly any votes. Two things seem to have happened: the turnout increased, and most of this increased turnout voted Labour, and the (small but significant) Lib Dem vote collapsed, with those voters probably either staying at home or voting Labour too.
The local Labour team did an excellent job of exploiting their own government's economic incompetence by running a largely anti-cuts message, and this appears to have resonated well with voters. But I don't believe that the Labour party, either locally or nationally, is offering a credible alternative, and that's why I'll keep fighting to represent the people of Quinton ward.