Westminster blues?

What are MPs for?  The theory is straightforward - they are there to represent their constituency in Parliament.  Does that mean that they should do what the people in their constituency want?  Problem - how do they know what they want?  Clearly there will be those who want one thing, and others who want something different. So - referendum?  The majority carries the day?  But then, why have an MP at all if he or she is simply going to announce the result as it were.  Anybody could do that - a computer program could be written to cope with that.  Surely we elect an MP to do what they consider is in our best interests - even if it is something we personally disagree with. Why am I going on like this?  Because it seems to me that Jeremy Corbyn, leader of the Labour Party, is intent on bypassing his MPs and putting his party's policy decisions in the hands of the party's national executive committee, who are of course elected by the party members, so not even representative of the electorate at large.  So. like I say - what's an MP for?