Except for the result of the election, the elector votes exactly the same way, he has an MP, and the campaign is the same. You have to be good locally, because it would be throughout. The only issue is the change in local election, which will create some frustration, at least in the first election. After two or three, the system will probably stabilize. If you change the voting system, it takes three elections to have the whole political system adjust. Don't cry after the first.
That would be my pitch—it's just the same thing, but proportional. We just correct the system.