Representing the Regions

This is old news now (a Miliband speech from October), but apparently I missed it at the time. I don't know whether it's official Labour policy - presumably their 2015 manifesto will make this clearer - but Labour are seemingly proposing a senate (second chamber) to 'represent the regions'. While I agree that the current Lords is unrepresentative, on this front and others, this seems like an odd choice of remedy.

First, why should regions be represented, rather than people? Israel, for example, has no regional constituencies but uses a nation-wide PR system. If it happens that people vote along regional lines, so be it, but other cleavages may be more important and there's no obvious reason why our political institutions ought to be designed around geography (the idea that 'all politics is local' may be a consequence of these institutions, rather than a justification for them - as Andrew Rehfeld argues).

Secondly, the House of Commons is already elected on a geographical basis, so presumably the regions are already represented there. If we're to have an elected second chamber, why not constitute it on some other basis? For instance, we could assign people to constituencies based on age or even randomly (again, Rehfeld's proposal).