Don't kid yourself. This is no principled stand. It's a publicity grab, pure and simple.
Mike Gapes, a career backbencher well into his sixties, was on the verge of tears at the press conference. The tendency to assume that the motivations of people who do something you oppose can only ever be base is dismal in the extreme. This mass-resignation might well turn out be a very bad idea, but it is clearly not a light thing for (at least most) of the people involved.
Strongly agree.
Suggesting that the MPs motives are personal not substantive is just a defense mechanism for some.