For 2: The Lords are appointed for life and therefore cannot be removed from office.
For 3: The Lords are useless and get overridden by the Commons. We need a chamber with power.
For 4: It is anachronistic for a democratic state to have an unelected chamber of parliament.
For 5: But it's WRONG.
Against 1: The Commons represents the nation: a second chamber in a unitary state cannot duplicate this effect, as it would be both absurd and constitutionally harmful.
Against 2: Their life appointment means they do not have to constantly look over their shoulders at the ballot box and vote the way the party wants them or to bend to populist demands. Their concern is for what makes sense legislatively, not what is popular.
Against 3: Firstly, the Lords does more valuable work for parliamentary scrutiny in the UK than an elected House could do, simply because the Commons doesn't have the time to do it in their legislative timetable, and they are thoroughly bullied by party leaders into not asking uncomfortable questions, unless they are prepared to lose their party's support over it. Secondly, from foreign examples, election does not come with power; there are many second chambers, which are more impotent than the Lords.
Against 4: Says who? Never judge your system on some arbitrary calendar. If it works, it works. An elected House would cause untold damage and fix an imaginary problem that doesn't need repairing.
Against 5: Boo frickin' hoo.
The Lord long ago ceased to be a hereditary chamber. It's a House of experts immune from party leadership pressure and does superior work to the Commons.
AND FINALLY: Caliban makes the mistake of assuming that an elected second chamber is automatically superior to an appointed chamber of experts. Well, there are a few strong and effective second chambers, namely the German Bundesrat and the Australian and US