The moment an MP is allowed to state that s/he will "vote his/her conscience" and not the wished of the voters; it is a long slippery slope down to the subversion of democracy.
I believe you're not over-keen on them, but perhaps we need more referenda, Suff, like the Swiss model which has a binding force on legislators.
Here in Birmingham, we decisively voted against the imposition of a Lord Mayor backalong, and at a more micro-level, I believe we are shortly going to have a referendum in Sutton Coldfield as to whether or not we declare a sort of UDI from Birmingham and revert to a town council. (This is largely because most of our middle-class council tax is getting diverted to inner-city projects which isn't going down too well ..... )