Firstly - What I don't understand is how the system allows for individual votes at all if they need to be beholden to the party.  The argument that MP's are not free agents falls flat when we know they are entitled to individual votes.

Secondly - if we accept that they must be free agents or to choose to be free agents then we do need to have a systematic way to cater for real issues of intimidation and threat that would prevent MPs exercising their free vote.  To use an extreme example to make a point - if the MPs were under threat of death surely we would need a way to prevent or attempt to mitigate this risk... if agreed then where is the point where it is an unacceptable threat... is party intimidation not unacceptable?