What you seem to be suggesting, fly, is that if the total percentage of votes cast nationally was, say, Labour 45%, Tory 40%, Lib Dem 15%; then the 659 seats in Parliament should be allocated pro rata with those percentages. That might appear to be a fair way of allocating seats, but there would then be the problem of (a) choosing individuals to occupy those seats (presumably the national parties would have to choose them); and (b) the bigger problem of establishing some sort of link between the electorate and MPs - ie the link now provided by MPs representing constituencies, so we each know who "our" MP is. Such an electoral system would probably result in an enormous increase in the power of party central offices, and even greater apathy amongst the electorate than there is today.