The Whip system should immediately be dismantled, it is both immensely anti-democratic as well as immensely dangerous when you get bad policy, bad ministers (or both - as happened in 1940, and during the buildup to Iraq). If one looks at the Lords - where the Whips have hardly any power, by comparison - their decisions and amendments are nearly always much better, and the debates more well-informed.
MPs should not - indeed, must not - be subjected to any pressure from anyone but their electors or the law. They should vote according to their beliefs based on the facts and be judged accordingly come election-time. It is because they do not, and are not, that this country is in the mess that it is in.