House of Lords
Now that the Commons have voted to create a wholly elected House of Lords, perhaps I could suggest another solution to prevent two almost identical chambers?
What about letting all councils (county councils, district councils and unitary authorities) appoint one representative each, and then add representatives from the parliaments/assemblies of Scotland, Wales, Northern Ireland and London, and finally add all the UK members of the European Parliament.
In this way, the Lords would provide a very different view from the Commons, and it would be a strong guardian against the centralising instincts of government.